feat: season filter + chart bands on Dashboard and Comparison

Dashboard:
- Season dropdown filter (filters data by season date range)
- Revenue trend chart shows colored annotation bands for each season
- All downstream memos use season-filtered data

Comparison:
- Season presets in period selector (optgroup)
- Auto-compares with same season from previous hijri year if defined
- Season preset persists start/end dates in URL

Added chartjs-plugin-annotation for chart bands.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/Comparison.tsx

@@ -17,7 +17,7 @@ import {
   getMuseumsForDistrict,
   getLatestYear
 } from '../services/dataService';
-import type { MuseumRecord, ComparisonProps, DateRangeFilters } from '../types';
+import type { MuseumRecord, ComparisonProps, DateRangeFilters, Season } from '../types';
 
 interface PresetDateRange {
   start: string;
@@ -63,7 +63,7 @@ const generatePresetDates = (year: number): PresetDates => ({
   'full': { start: `${year}-01-01`, end: `${year}-12-31` }
 });
 
-function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIncludeVAT }: ComparisonProps) {
+function Comparison({ data, seasons, showDataLabels, setShowDataLabels, includeVAT, setIncludeVAT }: ComparisonProps) {
   const { t } = useLanguage();
   const [searchParams, setSearchParams] = useSearchParams();
   
@@ -95,7 +95,10 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
     if (urlPreset && urlPreset !== 'custom' && dates[urlPreset]) {
       return dates[urlPreset].start;
     }
-    return searchParams.get('from') || `${year}-01-01`;
+    // Season presets store from/to in URL
+    const fromParam = searchParams.get('from');
+    if (fromParam) return fromParam;
+    return `${year}-01-01`;
   });
   const [endDate, setEndDateState] = useState(() => {
     const urlPreset = searchParams.get('preset');
@@ -105,7 +108,10 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
     if (urlPreset && urlPreset !== 'custom' && dates[urlPreset]) {
       return dates[urlPreset].end;
     }
-    return searchParams.get('to') || `${year}-01-31`;
+    // Season presets store from/to in URL
+    const toParam = searchParams.get('to');
+    if (toParam) return toParam;
+    return `${year}-01-31`;
   });
   const [filters, setFiltersState] = useState(() => ({
     district: searchParams.get('district') || 'all',
@@ -123,7 +129,7 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
     const params = new URLSearchParams();
     if (newPreset && newPreset !== 'jan') params.set('preset', newPreset);
     if (newYear && newYear !== latestYear) params.set('year', newYear.toString());
-    if (newPreset === 'custom') {
+    if (newPreset === 'custom' || newPreset.startsWith('season-')) {
       if (newFrom) params.set('from', newFrom);
       if (newTo) params.set('to', newTo);
     }
@@ -136,7 +142,7 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
   const setSelectedYear = (year: number) => {
     setSelectedYearState(year);
     const newDates = generatePresetDates(year);
-    if (preset !== 'custom' && newDates[preset]) {
+    if (preset !== 'custom' && !preset.startsWith('season-') && newDates[preset]) {
       setStartDateState(newDates[preset].start);
       setEndDateState(newDates[preset].end);
     }
@@ -145,7 +151,15 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
 
   const setPreset = (value: string) => {
     setPresetState(value);
-    if (value !== 'custom' && presetDates[value]) {
+    if (value.startsWith('season-')) {
+      const seasonId = parseInt(value.replace('season-', ''));
+      const season = seasons.find(s => s.Id === seasonId);
+      if (season) {
+        setStartDateState(season.StartDate);
+        setEndDateState(season.EndDate);
+        updateUrl(value, season.StartDate, season.EndDate, filters, selectedYear);
+      }
+    } else if (value !== 'custom' && presetDates[value]) {
       setStartDateState(presetDates[value].start);
       setEndDateState(presetDates[value].end);
       updateUrl(value, null, null, filters, selectedYear);
@@ -227,13 +241,29 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
   const availableMuseums = useMemo(() => getMuseumsForDistrict(data, filters.district), [data, filters.district]);
 
   // Year-over-year comparison: same dates, previous year
-  const ranges = useMemo(() => ({
-    curr: { start: startDate, end: endDate },
-    prev: { 
+  // For season presets, try to find the same season name from the previous hijri year
+  const ranges = useMemo(() => {
+    const curr = { start: startDate, end: endDate };
+    let prev = {
       start: startDate.replace(/^(\d{4})/, (_: string, y: string) => String(parseInt(y) - 1)),
       end: endDate.replace(/^(\d{4})/, (_: string, y: string) => String(parseInt(y) - 1))
+    };
+
+    if (preset.startsWith('season-')) {
+      const seasonId = parseInt(preset.replace('season-', ''));
+      const currentSeason = seasons.find(s => s.Id === seasonId);
+      if (currentSeason) {
+        const prevSeason = seasons.find(
+          s => s.Name === currentSeason.Name && s.HijriYear === currentSeason.HijriYear - 1
+        );
+        if (prevSeason) {
+          prev = { start: prevSeason.StartDate, end: prevSeason.EndDate };
+        }
+      }
     }
-  }), [startDate, endDate]);
+
+    return { curr, prev };
+  }, [startDate, endDate, preset, seasons]);
 
   const prevData = useMemo(() => 
     filterDataByDateRange(data, ranges.prev.start, ranges.prev.end, filters),
@@ -559,9 +589,18 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
               <option value="h1">{t('time.h1')}</option>
               <option value="h2">{t('time.h2')}</option>
               <option value="full">{t('time.fullYear')}</option>
+              {seasons.length > 0 && (
+                <optgroup label={t('comparison.seasons') || 'Seasons'}>
+                  {seasons.map(s => (
+                    <option key={s.Id} value={`season-${s.Id}`}>
+                      {s.Name} {s.HijriYear}
+                    </option>
+                  ))}
+                </optgroup>
+              )}
             </select>
           </FilterControls.Group>
-          {preset !== 'custom' && (
+          {preset !== 'custom' && !preset.startsWith('season-') && (
             <FilterControls.Group label={t('filters.year')}>
               <select value={selectedYear} onChange={e => setSelectedYear(parseInt(e.target.value))}>
                 {availableYears.map(y => (
@@ -570,7 +609,7 @@ function Comparison({ data, showDataLabels, setShowDataLabels, includeVAT, setIn
               </select>
             </FilterControls.Group>
           )}
-          {preset === 'custom' && (
+          {(preset === 'custom' || preset.startsWith('season-')) && (
             <>
               <FilterControls.Group label={t('comparison.from')}>
                 <input type="date" value={startDate} onChange={e => setStartDate(e.target.value)} />