fix: responsive, ARIA, performance and CSS cleanup improvements

Addresses remaining medium and low severity audit findings:

- H2: Dark mode @media selector narrowed to :root:not([data-theme]) so
  OS-preference and manual-override blocks are now mutually exclusive
- L2: Remove ~410 lines of dead Slides Builder CSS (no component exists)
- M2: VAT toggle uses flex spacer instead of margin-inline-start:auto,
  preventing layout break when filter bar wraps at medium-small widths
- M3: Page content max-width aligned to 1400px (matches nav bar)
- M5: Period picker toggle now has aria-controls="period-picker-panel"
  pointing to the InlinePicker root in both Dashboard and Comparison
- M6: Offline badge cache timestamp exposed via sr-only span for
  screen reader accessibility (was title-only before)
- M7: chartOpts/barHorizOpts/barNoLegend wrapped in useMemo([baseOpts])
  to prevent unnecessary Chart.js re-renders
- L4: Filter bar scrolls horizontally on mobile instead of wrapping
- L5: Metrics grid uses auto-fit/minmax to eliminate orphaned cards

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/App.css

@@ -48,9 +48,9 @@
   --bg-tertiary: var(--border);
 }
 
-/* Dark mode */
+/* OS dark preference — only when no manual theme is set */
 @media (prefers-color-scheme: dark) {
-  :root:not([data-theme="light"]) {
+  :root:not([data-theme]) {
     --bg: #0f172a;
     --surface: #1e293b;
     --border: #334155;
@@ -80,7 +80,7 @@
   }
 }
 
-/* Manual theme override */
+/* Explicit dark theme (user preference overrides OS) */
 :root[data-theme="dark"] {
   --bg: #0f172a;
   --surface: #1e293b;
@@ -2322,416 +2322,6 @@ tr.editing td {
   }
 }
 
-/* ========== Slides Builder ========== */
-.slides-builder {
-  padding: 24px;
-  max-width: 1400px;
-  margin: 0 auto;
-}
-
-.slides-toolbar {
-  display: flex;
-  gap: 12px;
-  margin-bottom: 24px;
-  flex-wrap: wrap;
-}
-
-.btn-primary, .btn-secondary {
-  display: inline-flex;
-  align-items: center;
-  gap: 8px;
-  padding: 10px 18px;
-  border-radius: 8px;
-  font-size: 14px;
-  font-weight: 500;
-  cursor: pointer;
-  transition: all 0.15s ease;
-  border: none;
-}
-
-.btn-primary {
-  background: var(--accent);
-  color: var(--text-inverse);
-}
-
-.btn-primary:hover {
-  background: var(--accent);
-}
-
-.btn-secondary {
-  background: var(--bg-secondary);
-  color: var(--text-primary);
-  border: 1px solid var(--border);
-}
-
-.btn-secondary:hover {
-  background: var(--bg-tertiary);
-}
-
-.slides-workspace {
-  display: grid;
-  grid-template-columns: 280px 1fr;
-  gap: 24px;
-  min-height: 600px;
-}
-
-.slides-list {
-  background: var(--bg-secondary);
-  border-radius: 12px;
-  padding: 16px;
-  border: 1px solid var(--border);
-}
-
-.slides-list h3 {
-  font-size: 14px;
-  color: var(--text-secondary);
-  margin-bottom: 16px;
-  font-weight: 500;
-}
-
-.empty-slides {
-  text-align: center;
-  padding: 40px 20px;
-  color: var(--text-secondary);
-}
-
-.empty-slides button {
-  margin-top: 16px;
-  padding: 8px 16px;
-  background: var(--accent);
-  color: var(--text-inverse);
-  border: none;
-  border-radius: 6px;
-  cursor: pointer;
-}
-
-.slides-thumbnails {
-  display: flex;
-  flex-direction: column;
-  gap: 8px;
-}
-
-.slide-thumbnail {
-  display: grid;
-  grid-template-columns: 32px 32px 1fr auto;
-  align-items: center;
-  gap: 8px;
-  padding: 12px;
-  background: var(--bg-primary);
-  border-radius: 8px;
-  cursor: pointer;
-  transition: all 0.15s ease;
-  border: 2px solid transparent;
-}
-
-.slide-thumbnail:hover {
-  border-color: var(--border);
-}
-
-.slide-thumbnail.active {
-  border-color: var(--accent);
-  background: rgba(59, 130, 246, 0.05);
-}
-
-.slide-thumbnail .slide-number {
-  width: 24px;
-  height: 24px;
-  background: var(--bg-tertiary);
-  border-radius: 6px;
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  font-size: 12px;
-  font-weight: 600;
-  color: var(--text-secondary);
-}
-
-.slide-thumbnail .slide-icon {
-  font-size: 18px;
-}
-
-.slide-thumbnail .slide-title-preview {
-  font-size: 13px;
-  font-weight: 500;
-  white-space: nowrap;
-  overflow: hidden;
-  text-overflow: ellipsis;
-}
-
-.slide-thumbnail .slide-actions {
-  display: flex;
-  gap: 4px;
-  opacity: 0;
-  transition: opacity 0.15s ease;
-}
-
-.slide-thumbnail:hover .slide-actions {
-  opacity: 1;
-}
-
-.slide-actions button {
-  width: 24px;
-  height: 24px;
-  border: none;
-  background: var(--bg-tertiary);
-  border-radius: 4px;
-  cursor: pointer;
-  font-size: 12px;
-  color: var(--text-secondary);
-}
-
-.slide-actions button:hover {
-  background: var(--border);
-}
-
-.slide-actions button.delete:hover {
-  background: var(--danger-light);
-  color: var(--danger);
-}
-
-/* Slide Editor */
-.slide-editor {
-  background: var(--bg-secondary);
-  border-radius: 12px;
-  padding: 24px;
-  border: 1px solid var(--border);
-}
-
-.editor-section {
-  margin-bottom: 20px;
-}
-
-.editor-section label {
-  display: block;
-  font-size: 13px;
-  font-weight: 500;
-  color: var(--text-secondary);
-  margin-bottom: 8px;
-}
-
-.editor-section input[type="text"],
-.editor-section input[type="date"],
-.editor-section select {
-  width: 100%;
-  padding: 10px 12px;
-  border: 1px solid var(--border);
-  border-radius: 8px;
-  font-size: 14px;
-  background: var(--bg-primary);
-  color: var(--text-primary);
-}
-
-.editor-section input:focus,
-.editor-section select:focus {
-  outline: 2px solid var(--accent);
-  outline-offset: -1px;
-  border-color: var(--accent);
-}
-
-.editor-row {
-  display: grid;
-  grid-template-columns: 1fr 1fr;
-  gap: 16px;
-}
-
-.chart-type-grid {
-  display: grid;
-  grid-template-columns: repeat(2, 1fr);
-  gap: 8px;
-}
-
-.chart-type-btn {
-  display: flex;
-  flex-direction: column;
-  align-items: center;
-  gap: 6px;
-  padding: 16px 12px;
-  border: 2px solid var(--border);
-  border-radius: 10px;
-  background: var(--bg-primary);
-  cursor: pointer;
-  transition: all 0.15s ease;
-}
-
-.chart-type-btn:hover {
-  border-color: var(--accent);
-}
-
-.chart-type-btn.active {
-  border-color: var(--accent);
-  background: rgba(59, 130, 246, 0.05);
-}
-
-.chart-type-btn .chart-icon {
-  font-size: 24px;
-}
-
-.chart-type-btn span:last-child {
-  font-size: 12px;
-  font-weight: 500;
-  color: var(--text-secondary);
-}
-
-.slide-preview-box {
-  margin-top: 24px;
-  padding-top: 24px;
-  border-top: 1px solid var(--border);
-}
-
-.slide-preview-box h4 {
-  font-size: 13px;
-  font-weight: 500;
-  color: var(--text-secondary);
-  margin-bottom: 16px;
-}
-
-.preview-chart {
-  background: var(--bg-primary);
-  border-radius: 8px;
-  padding: 16px;
-  height: 200px;
-}
-
-.preview-kpis {
-  display: grid;
-  grid-template-columns: repeat(3, 1fr);
-  gap: 12px;
-}
-
-.preview-kpi {
-  background: var(--bg-primary);
-  border-radius: 8px;
-  padding: 16px;
-  text-align: center;
-}
-
-.preview-kpi .kpi-value {
-  font-size: 1.5rem;
-  font-weight: 700;
-  color: var(--accent);
-}
-
-.preview-kpi .kpi-label {
-  font-size: 12px;
-  color: var(--text-secondary);
-  margin-top: 4px;
-}
-
-/* Preview Fullscreen */
-.preview-fullscreen {
-  position: fixed;
-  top: 0;
-  left: 0;
-  right: 0;
-  bottom: 0;
-  background: linear-gradient(135deg, var(--text-primary) 0%, var(--dark-surface) 100%);
-  z-index: 1000;
-  display: flex;
-  flex-direction: column;
-}
-
-.preview-slide {
-  flex: 1;
-  display: flex;
-  flex-direction: column;
-  align-items: center;
-  justify-content: center;
-  padding: 60px;
-}
-
-.preview-title {
-  color: var(--bg);
-  font-size: 2.5rem;
-  font-weight: 600;
-  margin-bottom: 40px;
-  text-align: center;
-}
-
-.preview-content {
-  width: 100%;
-  max-width: 900px;
-}
-
-.preview-content .preview-chart {
-  height: 350px;
-  background: rgba(255, 255, 255, 0.03);
-  border-radius: 16px;
-  padding: 30px;
-}
-
-.preview-content .preview-kpis .preview-kpi {
-  background: rgba(255, 255, 255, 0.05);
-  padding: 30px;
-}
-
-.preview-content .preview-kpis .kpi-value {
-  font-size: 2.5rem;
-}
-
-.preview-content .preview-kpis .kpi-label {
-  color: var(--dark-muted);
-}
-
-.preview-footer {
-  color: var(--text-muted);
-  font-size: 14px;
-  margin-top: 40px;
-}
-
-.preview-controls {
-  display: flex;
-  justify-content: center;
-  gap: 12px;
-  padding: 20px;
-  background: rgba(0, 0, 0, 0.3);
-}
-
-.preview-controls button {
-  padding: 10px 24px;
-  background: rgba(255, 255, 255, 0.1);
-  color: var(--text-inverse);
-  border: none;
-  border-radius: 8px;
-  cursor: pointer;
-  font-size: 14px;
-}
-
-.preview-controls button:hover:not(:disabled) {
-  background: rgba(255, 255, 255, 0.2);
-}
-
-.preview-controls button:disabled {
-  opacity: 0.3;
-  cursor: not-allowed;
-}
-
-@media (max-width: 768px) {
-  .slides-workspace {
-    grid-template-columns: 1fr;
-  }
-  
-  .slides-list {
-    max-height: 200px;
-    overflow-y: auto;
-  }
-  
-  .editor-row {
-    grid-template-columns: 1fr;
-  }
-  
-  .chart-type-grid {
-    grid-template-columns: repeat(4, 1fr);
-  }
-  
-  .preview-slide {
-    padding: 30px;
-  }
-  
-  .preview-title {
-    font-size: 1.5rem;
-  }
-}
-
 /* Chart Export Button & Header */
 .exportable-chart-wrapper {
   position: relative;

src/App.tsx

@@ -250,6 +250,11 @@ function App() {
                     <line x1="12" y1="20" x2="12.01" y2="20"/>
                   </svg>
                   {t('app.offline') || 'Offline'}
+                  {cacheInfo && (
+                    <span className="sr-only">
+                      {` (cached ${new Date(cacheInfo.timestamp || '').toLocaleString()})`}
+                    </span>
+                  )}
                 </span>
               )}
               <button

src/components/Comparison.tsx

@@ -197,7 +197,7 @@ function InlinePicker({ start, end, onChange, onClose, availableYears, L }: {
   };
 
   return (
-    <div className="alt-picker">
+    <div className="alt-picker" id="period-picker-panel">
       <div className="alt-picker-year">
         <button type="button" onClick={() => shift(L.dir==='rtl' ? 1 : -1)} disabled={L.dir==='rtl' ? year>=maxY : year<=minY} className="alt-yr-btn">
           <svg width="7" height="11" viewBox="0 0 7 11" fill="none"><path d="M5.5 9.5L1.5 5.5L5.5 1.5" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round"/></svg>
@@ -262,7 +262,7 @@ function PeriodCard({ role, hint, start, end, variant, onChange, availableYears,
         </div>
         <div className="alt-period-name">{periodNameL(start, end, L)}</div>
         <div className="alt-date-range">{dateRangeTextL(start, end, L)}</div>
-        <button type="button" className="alt-change-btn" onClick={() => setOpen(v => !v)} aria-expanded={open}>
+        <button type="button" className="alt-change-btn" onClick={() => setOpen(v => !v)} aria-expanded={open} aria-controls="period-picker-panel">
           {open ? L.close : L.changePeriod}
           <svg width="10" height="10" viewBox="0 0 10 10" fill="none" style={{ transform:open?'rotate(180deg)':'none', transition:'transform 0.2s' }}>
             <path d="M2 3.5L5 6.5L8 3.5" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round"/>
@@ -443,7 +443,10 @@ export default function PeriodSelectorDemo({ data, seasons, includeVAT, allowedM
   }, [data, prevData, currData, prevStart, prevEnd, currStart, currEnd, metric, getVal]);
 
   const baseOpts = useMemo(() => createBaseOptions(false), []);
-  const chartOpts: any = { ...baseOpts, plugins:{ ...baseOpts.plugins, legend:{ position:'top', align:'end', labels:{ boxWidth:12, padding:12 } } } };
+  const { chartOpts } = useMemo(() => {
+    const chartOpts: any = { ...baseOpts, plugins:{ ...baseOpts.plugins, legend:{ position:'top', align:'end', labels:{ boxWidth:12, padding:12 } } } };
+    return { chartOpts };
+  }, [baseOpts]);
 
   const metricOpts = [
     { value:'revenue', label:L.revenue }, { value:'visitors', label:L.visitors },
@@ -477,7 +480,7 @@ export default function PeriodSelectorDemo({ data, seasons, includeVAT, allowedM
       <style>{`
         ${L.fontImport}
 
-        .alt-page { max-width:1100px; margin:0 auto; padding:48px 24px 80px; font-family:${L.bodyFont}; width:100%; box-sizing:border-box; }
+        .alt-page { max-width:1400px; margin:0 auto; padding:48px 24px 80px; font-family:${L.bodyFont}; width:100%; box-sizing:border-box; }
 
         /* ── header ── */
         .alt-back { display:inline-flex; align-items:center; gap:6px; font-size:.8125rem; color:var(--text-muted); text-decoration:none; margin-bottom:28px; transition:color .15s; }
@@ -572,7 +575,7 @@ export default function PeriodSelectorDemo({ data, seasons, includeVAT, allowedM
         .alt-filter-reset:hover { color:var(--danger); }
 
         /* ── metrics ── */
-        .alt-metrics { display:grid; grid-template-columns:repeat(3,1fr); gap:1px; background:var(--border); border:1px solid var(--border); border-radius:var(--radius); overflow:hidden; margin-bottom:40px; }
+        .alt-metrics { display:grid; grid-template-columns:repeat(auto-fit,minmax(200px,1fr)); gap:1px; background:var(--border); border:1px solid var(--border); border-radius:var(--radius); overflow:hidden; margin-bottom:40px; }
         .alt-metric { background:var(--surface); padding:24px 22px; }
         .alt-metric-title { font-size:.6875rem; font-weight:700; text-transform:uppercase; letter-spacing:.08em; color:var(--text-muted); margin:0 0 12px; }
         .alt-metric-value { font-family:${L.displayFont}; font-size:1.875rem; font-weight:400; color:var(--text-primary); line-height:1; margin-bottom:10px; letter-spacing:-.02em; }
@@ -612,6 +615,13 @@ export default function PeriodSelectorDemo({ data, seasons, includeVAT, allowedM
           .alt-chart-header { flex-direction:column; }
         }
 
+        @media (max-width:700px) {
+          .alt-filter-bar { overflow-x:auto; flex-wrap:nowrap; padding-inline:12px; -webkit-overflow-scrolling:touch; }
+          .altms-trigger { flex-shrink:0; }
+          .alt-vat-toggle { flex-shrink:0; }
+          .alt-filter-spacer { display:none; }
+        }
+
         /* ── focus-visible ── */
         .alt-chip:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
         .alt-ctrl:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

src/components/Dashboard.tsx

@@ -204,7 +204,7 @@ function InlinePicker({ start, end, onChange, onClose, availableYears, L }: {
   };
 
   return (
-    <div className="alt-picker">
+    <div className="alt-picker" id="period-picker-panel">
       <div className="alt-picker-year">
         <button type="button" onClick={() => shift(L.dir==='rtl' ? 1 : -1)} disabled={L.dir==='rtl' ? year>=maxY : year<=minY} className="alt-yr-btn">
           <svg width="7" height="11" viewBox="0 0 7 11" fill="none"><path d="M5.5 9.5L1.5 5.5L5.5 1.5" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round"/></svg>
@@ -264,7 +264,7 @@ function PeriodHero({ start, end, onChange, availableYears, L }: {
           <div className="dalt-hero-name">{periodNameL(start, end, L)}</div>
           <div className="dalt-hero-range">{dateRangeTextL(start, end, L)}</div>
         </div>
-        <button type="button" className="dalt-hero-btn" onClick={() => setOpen(v => !v)} aria-expanded={open}>
+        <button type="button" className="dalt-hero-btn" onClick={() => setOpen(v => !v)} aria-expanded={open} aria-controls="period-picker-panel">
           {open ? L.close : L.changePeriod}
           <svg width="10" height="10" viewBox="0 0 10 10" fill="none" style={{ transform: open?'rotate(180deg)':'none', transition:'transform 0.2s' }}>
             <path d="M2 3.5L5 6.5L8 3.5" stroke="currentColor" strokeWidth="1.5" strokeLinecap="round" strokeLinejoin="round"/>
@@ -481,9 +481,12 @@ export default function DashboardDemo({ data, seasons: _seasons, includeVAT, set
   const prevCapture  = prevPilgrims ? prevM.visitors/prevPilgrims*100 : null;
 
   const baseOpts  = useMemo(() => createBaseOptions(false), []);
-  const chartOpts: any = { ...baseOpts, plugins:{ ...baseOpts.plugins, legend:{ position:'top', align:'end', labels:{ boxWidth:10, padding:10, font:{ size:11 } } } } };
+  const { chartOpts, barHorizOpts, barNoLegend } = useMemo(() => {
-  const barHorizOpts: any = { ...chartOpts, indexAxis:'y', plugins:{ ...chartOpts.plugins, legend:{ display:false } } };
+    const chartOpts: any = { ...baseOpts, plugins:{ ...baseOpts.plugins, legend:{ position:'top', align:'end', labels:{ boxWidth:10, padding:10, font:{ size:11 } } } } };
-  const barNoLegend: any  = { ...chartOpts, plugins:{ ...chartOpts.plugins, legend:{ display:false } } };
+    const barHorizOpts: any = { ...chartOpts, indexAxis:'y', plugins:{ ...chartOpts.plugins, legend:{ display:false } } };
+    const barNoLegend: any  = { ...chartOpts, plugins:{ ...chartOpts.plugins, legend:{ display:false } } };
+    return { chartOpts, barHorizOpts, barNoLegend };
+  }, [baseOpts]);
   const pieOptions: any = useMemo(() => ({
     responsive: true, maintainAspectRatio: false,
     plugins: {
@@ -502,7 +505,7 @@ export default function DashboardDemo({ data, seasons: _seasons, includeVAT, set
       <style>{`
         ${L.fontImport}
 
-        .alt-page { max-width:1100px; margin:0 auto; padding:48px 24px 80px; font-family:${L.bodyFont}; width:100%; box-sizing:border-box; }
+        .alt-page { max-width:1400px; margin:0 auto; padding:48px 24px 80px; font-family:${L.bodyFont}; width:100%; box-sizing:border-box; }
 
         /* ── header ── */
         .alt-back { display:inline-flex; align-items:center; gap:6px; font-size:.8125rem; color:var(--text-muted); text-decoration:none; margin-bottom:28px; transition:color .15s; }
@@ -571,14 +574,15 @@ export default function DashboardDemo({ data, seasons: _seasons, includeVAT, set
         .alt-filter-bar { display:flex; gap:8px; flex-wrap:wrap; align-items:center; margin-bottom:32px; padding:14px 20px; background:var(--surface); border:1px solid var(--border); border-radius:var(--radius); }
         .alt-filter-label { font-size:.6875rem; font-weight:700; text-transform:uppercase; letter-spacing:.08em; color:var(--text-muted); white-space:nowrap; }
         .alt-filter-sep { width:1px; height:20px; background:var(--border); flex-shrink:0; }
-        .alt-vat-toggle { margin-inline-start:auto; display:flex; align-items:center; border:1px solid var(--border); border-radius:8px; overflow:hidden; }
+        .alt-filter-spacer { flex:1; min-width:0; }
+        .alt-vat-toggle { display:flex; align-items:center; border:1px solid var(--border); border-radius:8px; overflow:hidden; }
         .alt-vat-opt { font-family:${L.bodyFont}; font-size:.75rem; font-weight:500; padding:5px 10px; background:var(--surface); color:var(--text-muted); cursor:pointer; border:none; transition:background .1s,color .1s; }
         .alt-vat-opt--on { background:var(--accent); color:var(--text-inverse); }
         .alt-filter-reset { font-size:.8125rem; color:var(--text-muted); background:none; border:none; cursor:pointer; padding:4px 6px; transition:color .15s; font-family:${L.bodyFont}; }
         .alt-filter-reset:hover { color:var(--danger); }
 
         /* ── metrics ── */
-        .alt-metrics { display:grid; grid-template-columns:repeat(3,1fr); gap:1px; background:var(--border); border:1px solid var(--border); border-radius:var(--radius); overflow:hidden; margin-bottom:40px; }
+        .alt-metrics { display:grid; grid-template-columns:repeat(auto-fit,minmax(200px,1fr)); gap:1px; background:var(--border); border:1px solid var(--border); border-radius:var(--radius); overflow:hidden; margin-bottom:40px; }
         .alt-metric { background:var(--surface); padding:24px 22px; }
         .alt-metric-title { font-size:.6875rem; font-weight:700; text-transform:uppercase; letter-spacing:.08em; color:var(--text-muted); margin:0 0 12px; }
         .alt-metric-value { font-family:${L.displayFont}; font-size:1.875rem; font-weight:400; color:var(--text-primary); line-height:1; margin-bottom:10px; letter-spacing:-.02em; }
@@ -616,6 +620,10 @@ export default function DashboardDemo({ data, seasons: _seasons, includeVAT, set
           .alt-metrics { grid-template-columns:1fr 1fr; }
           .alt-page-title { font-size:1.75rem; }
           .altms-label { max-width:100px; }
+          .alt-filter-bar { overflow-x:auto; flex-wrap:nowrap; padding-inline:12px; -webkit-overflow-scrolling:touch; }
+          .altms-trigger { flex-shrink:0; }
+          .alt-vat-toggle { flex-shrink:0; }
+          .alt-filter-spacer { display:none; }
         }
 
         /* ── focus-visible ── */
@@ -640,6 +648,7 @@ export default function DashboardDemo({ data, seasons: _seasons, includeVAT, set
         <AltMultiSelect value={selChannels}  options={allChannels}  onChange={setSelChannels}  allLabel={L.allChannels}  countLabel={L.countChannels}  clearLabel={L.clearSel} />
         <AltMultiSelect value={selMuseums}   options={allMuseums}   onChange={setSelMuseums}   allLabel={L.allMuseums}   countLabel={L.countMuseums}   clearLabel={L.clearSel} />
         {hasFilters && <button type="button" className="alt-filter-reset" onClick={() => { setSelDistricts([]); setSelChannels([]); setSelMuseums([]); }}>{L.reset}</button>}
+        <div className="alt-filter-spacer" />
         <div className="alt-vat-toggle">
           <button type="button" className={`alt-vat-opt${!includeVAT?' alt-vat-opt--on':''}`} onClick={() => setIncludeVAT(false)}>{L.exclVAT}</button>
           <button type="button" className={`alt-vat-opt${includeVAT ?' alt-vat-opt--on':''}`} onClick={() => setIncludeVAT(true)}>{L.inclVAT}</button>