Improve drag/swipe handling and Features page UX

- SwipeTabs: Delay pointer capture until drag starts for better tap detection
- Features: Only allow drag via handle dots, not entire card
- Features: Smart hasOrderChanges - hide buttons when order returns to initial
- Features: Don't apply dragging style until movement exceeds threshold
- ThemeSettings: Add role="button" for accessibility on all option cards
- Sidebar: Light theme active menu item styling improvements
- Layout: Tab bar translucency and blur effects

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/styles/Layout.css

@@ -100,6 +100,14 @@ label,
   -ms-overflow-style: none;
 }
 
+@supports (color: color-mix(in srgb, black, transparent)) {
+  .page-tabs-slider,
+  .admin-tabs-slider {
+    background: color-mix(in srgb, var(--color-bg-elevated) 75%, transparent);
+    backdrop-filter: blur(20px) saturate(1.15);
+  }
+}
+
 .page-tabs-slider::-webkit-scrollbar,
 .admin-tabs-slider::-webkit-scrollbar {
   display: none;
@@ -791,7 +799,8 @@ label,
 @supports (color: color-mix(in srgb, black, white)) {
   [data-theme='dark'] .page-tabs-slider,
   [data-theme='dark'] .admin-tabs-slider {
-    background: color-mix(in srgb, var(--color-bg-sidebar) 95%, transparent);
+    background: color-mix(in srgb, var(--color-bg-sidebar) 72%, transparent);
+    backdrop-filter: blur(24px) saturate(1.2);
   }
 }