feat(flutter/admin): adminRequestsProvider with optimistic approve/reject

AsyncNotifier removes the row optimistically on approve/reject; rolls
back to the pre-mutation list on server error. Invalidates
adminCountsProvider so the landing badge stays accurate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/admin/admin_providers.dart

@@ -5,6 +5,7 @@ import '../api/endpoints/admin_quarantine.dart';
 import '../api/endpoints/admin_requests.dart';
 import '../api/endpoints/admin_users.dart';
 import '../library/library_providers.dart' show dioProvider;
+import '../models/admin_request.dart';
 
 final adminRequestsApiProvider = FutureProvider<AdminRequestsApi>((ref) async {
   return AdminRequestsApi(await ref.watch(dioProvider.future));
@@ -51,3 +52,40 @@ final adminCountsProvider = FutureProvider<AdminCounts>((ref) async {
     users: (results[2] as List).length,
   );
 });
+
+class AdminRequestsController extends AsyncNotifier<List<AdminRequest>> {
+  @override
+  Future<List<AdminRequest>> build() async {
+    final api = await ref.watch(adminRequestsApiProvider.future);
+    return api.list();
+  }
+
+  Future<void> approve(String id) async {
+    await _decide(id, (api) => api.approve(id));
+  }
+
+  Future<void> reject(String id) async {
+    await _decide(id, (api) => api.reject(id));
+  }
+
+  Future<void> _decide(
+    String id,
+    Future<void> Function(AdminRequestsApi api) action,
+  ) async {
+    final api = await ref.read(adminRequestsApiProvider.future);
+    final current = state.value ?? const <AdminRequest>[];
+    state = AsyncData(current.where((r) => r.id != id).toList());
+    try {
+      await action(api);
+      // Refresh landing badge.
+      ref.invalidate(adminCountsProvider);
+    } catch (e, st) {
+      state = AsyncData(current);
+      Error.throwWithStackTrace(e, st);
+    }
+  }
+}
+
+final adminRequestsProvider =
+    AsyncNotifierProvider<AdminRequestsController, List<AdminRequest>>(
+        AdminRequestsController.new);