refactor: comprehensive frontend review — consistency, a11y, code quality

- Replace event dispatchers with BookingContext (Hero, Header, FloatingContact)
- Add focus trap hook for modals (SignupModal, NewsModal)
- Extract shared components: CollapsibleSection, ConfirmDialog, PriceField, AdminSkeleton
- Add delete confirmation dialog to ArrayEditor
- Replace hardcoded colors (#050505, #0a0a0a, #c9a96e, #2ecc71) with theme tokens
- Add CSS variables --color-surface-deep/dark for consistent dark surfaces
- Improve contrast: muted text neutral-500 → neutral-400 in dark mode
- Fix modal z-index hierarchy (modals z-60, header z-50, floats z-40)
- Consolidate duplicate formatDate → shared formatting.ts
- Add useMemo to TeamProfile groupMap computation
- Fix typography: responsive price text in Pricing section
- Add ARIA labels/expanded to FAQ, OpenDay, ArrayEditor grip handles
- Hide number input spinners globally
- Reorder admin sidebar: Dashboard → SEO → Bookings → site section order
- Use shared PriceField in Open Day editor
- Fix schedule grid first time slot (09:00) clipped by container
- Fix pre-existing type errors (bookings, hero, db interfaces)

src/app/admin/hero/page.tsx

@@ -232,7 +232,7 @@ function VideoManager({
     });
   }, [slots]);
 
-  const totalSize = fileSizes.reduce((sum, s) => sum + (s || 0), 0);
+  const totalSize = fileSizes.reduce((sum: number, s) => sum + (s || 0), 0);
   const totalMb = totalSize / (1024 * 1024);
 
   function getLoadRating(mb: number): { label: string; color: string } {