Polish + Optimize: Clean metadata, remove !important, prune unused CSS

- Update theme-color to match brand (#f8fafc), fix stale CRA description
- Remove manifest.json and logo192.png references (not used)
- Replace !important on chart export buttons with higher specificity selectors
- Remove unused .skeleton-text and .skeleton-loading CSS classes
- Remove duplicate skeleton animation keyframes

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

src/App.css

@@ -153,26 +153,7 @@ html[dir="rtl"] {
   background: var(--accent-hover);
 }
 
-/* Skeleton Loader */
-.skeleton {
-  background: linear-gradient(90deg, var(--border) 25%, var(--bg) 50%, var(--border) 75%);
-  background-size: 200% 100%;
-  animation: skeleton-loading 1.5s infinite;
-  border-radius: 4px;
-}
 
-@keyframes skeleton-loading {
-  0% { background-position: 200% 0; }
-  100% { background-position: -200% 0; }
-}
-
-.skeleton-text {
-  height: 1em;
-  margin-bottom: 0.5em;
-}
-
-.skeleton-text.lg { height: 2em; width: 60%; }
-.skeleton-text.sm { height: 0.75em; width: 40%; }
 
 /* Navigation */
 .nav-bar {
@@ -1968,12 +1949,12 @@ html[dir="rtl"] .chart-header-with-export {
 }
 
 /* Download button - always top corner, outside normal flow */
-.chart-export-btn,
-.chart-export-btn.visible {
-  position: absolute !important;
-  top: 0 !important;
-  right: 0 !important;
-  left: auto !important;
+.exportable-chart-wrapper .chart-export-btn,
+.exportable-chart-wrapper .chart-export-btn.visible {
+  position: absolute;
+  top: 0;
+  right: 0;
+  left: auto;
   z-index: 10;
   width: 32px;
   height: 32px;
@@ -1990,10 +1971,10 @@ html[dir="rtl"] .chart-header-with-export {
   flex-shrink: 0;
 }
 
-html[dir="rtl"] .chart-export-btn,
-html[dir="rtl"] .chart-export-btn.visible {
-  right: auto !important;
-  left: 0 !important;
+html[dir="rtl"] .exportable-chart-wrapper .chart-export-btn,
+html[dir="rtl"] .exportable-chart-wrapper .chart-export-btn.visible {
+  right: auto;
+  left: 0;
 }
 
 .chart-export-btn:hover {