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/lib/api.ts

@@ -92,6 +92,27 @@ export const ticketsApi = {
       method: 'POST',
       body: JSON.stringify({ code, eventId }),
     }),
+
+  // Search tickets by name/email (for scanner manual search)
+  search: (query: string, eventId?: string) =>
+    fetchApi<{ tickets: TicketSearchResult[] }>('/api/tickets/search', {
+      method: 'POST',
+      body: JSON.stringify({ query, eventId }),
+    }),
+
+  // Get event check-in stats (for scanner header counter)
+  getCheckinStats: (eventId: string) =>
+    fetchApi<{ eventId: string; capacity: number; checkedIn: number; totalActive: number }>(
+      `/api/tickets/stats/checkin?eventId=${eventId}`
+    ),
+
+  // Live search tickets (GET - for scanner live search with debounce)
+  searchLive: (q: string, eventId?: string) => {
+    const params = new URLSearchParams();
+    params.set('q', q);
+    if (eventId) params.set('eventId', eventId);
+    return fetchApi<{ tickets: LiveSearchResult[] }>(`/api/tickets/search?${params}`);
+  },
   
   checkin: (id: string) =>
     fetchApi<{ ticket: Ticket & { attendeeName?: string }; event?: { id: string; title: string }; message: string }>(`/api/tickets/${id}/checkin`, {
@@ -508,6 +529,39 @@ export interface TicketValidationResult {
   error?: string;
 }
 
+export interface TicketSearchResult {
+  id: string;
+  qrCode: string;
+  attendeeName: string;
+  attendeeEmail?: string;
+  attendeePhone?: string;
+  status: string;
+  checkinAt?: string;
+  event?: {
+    id: string;
+    title: string;
+    startDatetime: string;
+    location: string;
+  } | null;
+}
+
+export interface LiveSearchResult {
+  ticket_id: string;
+  name: string;
+  email?: string;
+  status: string;
+  checked_in: boolean;
+  checkinAt?: string;
+  event_id: string;
+  qrCode: string;
+  event?: {
+    id: string;
+    title: string;
+    startDatetime: string;
+    location: string;
+  } | null;
+}
+
 export interface Payment {
   id: string;
   ticketId: string;