fix: dashboard counters refresh after status changes

When a booking status is changed, confirmed, or deleted in any tab,
the dashboard summary cards re-fetch to show updated counts. Previously
the dashboard was stale until page reload.

src/app/admin/bookings/McRegistrationsTab.tsx

@@ -13,7 +13,7 @@ interface McRegistration extends BaseBooking {
 interface McSlot { date: string; startTime: string }
 interface McItem { title: string; slots: McSlot[] }
 
-export function McRegistrationsTab({ filter }: { filter: BookingFilter }) {
+export function McRegistrationsTab({ filter, onDataChange }: { filter: BookingFilter; onDataChange?: () => void }) {
   const [regs, setRegs] = useState<McRegistration[]>([]);
   const [mcDates, setMcDates] = useState<Record<string, string>>({});
   const [loading, setLoading] = useState(true);
@@ -75,6 +75,7 @@ export function McRegistrationsTab({ filter }: { filter: BookingFilter }) {
       endpoint="/api/admin/mc-registrations"
       filter={filter}
       onItemsChange={setRegs}
+      onDataChange={onDataChange}
       groups={groups}
     />
   );