Mobile scanner redesign + backend live search

- Scanner page: fullscreen mobile-first layout, Scan/Search/Recent tabs
- Scan tab: auto-start camera, switch camera, vibration/sound feedback
- Valid/invalid fullscreen states, confirm check-in, auto-return to camera
- Search tab: live backend search (300ms debounce), tap card for detail + check-in
- Recent tab: last 20 check-ins, session counter
- Backend: GET /api/tickets/search (live search), GET /api/tickets/stats/checkin
- Admin layout: hide sidebar on scanner page; fix hooks order (no early return before useEffect)
- Back button to dashboard/events (staff → events, others → admin)
- API: searchLive, getCheckinStats, LiveSearchResult; PostgreSQL LOWER cast for UUID

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/context/AuthContext.tsx

@@ -21,6 +21,7 @@ interface AuthContextType {
   token: string | null;
   isLoading: boolean;
   isAdmin: boolean;
+  hasAdminAccess: boolean;
   login: (email: string, password: string) => Promise<void>;
   loginWithGoogle: (credential: string) => Promise<void>;
   loginWithMagicLink: (token: string) => Promise<void>;
@@ -177,6 +178,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   }, []);
 
   const isAdmin = user?.role === 'admin' || user?.role === 'organizer';
+  const hasAdminAccess = user?.role === 'admin' || user?.role === 'organizer' || user?.role === 'staff' || user?.role === 'marketing';
 
   return (
     <AuthContext.Provider
@@ -185,6 +187,7 @@ export function AuthProvider({ children }: { children: ReactNode }) {
         token, 
         isLoading, 
         isAdmin, 
+        hasAdminAccess,
         login, 
         loginWithGoogle,
         loginWithMagicLink,