feat: booking panel upgrade — refactor, notes, search, manual add, polling

Phase 1 — Refactor:
- Split monolith _shared.tsx into types.ts, BookingComponents, InlineNotes,
  GenericBookingsList, AddBookingModal, SearchBar (no more _ prefix)
- All 3 tabs use GenericBookingsList — shared status workflow, filters, archive

Phase 2 — Features:
- DB migration 13: add notes column to all booking tables
- Inline notes with amber highlight, auto-save 800ms debounce
- Confirm modal comment saves to notes field
- Manual add: 2 tabs (Занятие / Мероприятие), filters expired MCs, Open Day support
- Search bar: cross-table search by name/phone
- 10s polling for real-time updates (bookings page + sidebar badge)
- Status change marks booking as seen (fixes unread count on reset)
- Confirm modal stores human-readable group label instead of raw groupId
- Confirmed group bookings appear in Reminders tab

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

src/app/admin/layout.tsx

@@ -53,7 +53,7 @@ export default function AdminLayout({
   const [unreadTotal, setUnreadTotal] = useState(0);
   const isLoginPage = pathname === "/admin/login";
 
-  // Fetch unread counts — poll every 30s
+  // Fetch unread counts — poll every 10s
   useEffect(() => {
     if (isLoginPage) return;
     function fetchCounts() {
@@ -63,7 +63,7 @@ export default function AdminLayout({
         .catch(() => {});
     }
     fetchCounts();
-    const interval = setInterval(fetchCounts, 30000);
+    const interval = setInterval(fetchCounts, 10000);
     return () => clearInterval(interval);
   }, [isLoginPage]);