auto-claude: subtask-4-1 - Add gRPC client provider to providers.dart

Add grpcClientProvider to providers.dart for gRPC-based API access:
- Import GrpcCqrsApiClient and GrpcConfig from api layer
- Create grpcClientProvider using Provider.autoDispose for proper
  channel cleanup when no longer watched
- Inject authService for token management
- Register onDispose callback to shutdown gRPC channel resources

This follows the same pattern as the existing apiClientProvider while
adding proper resource management for gRPC connections.

Co-Authored-By: Claude <noreply@anthropic.com>

lib/providers/providers.dart

@@ -3,6 +3,8 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../api/types.dart';
 import '../api/client.dart';
+import '../api/grpc_client.dart';
+import '../api/grpc_config.dart';
 import '../api/openapi_config.dart';
 import '../services/auth_service.dart';
 import '../models/user_profile.dart';
@@ -21,6 +23,31 @@ final apiClientProvider = Provider<CqrsApiClient>((ref) {
   );
 });
 
+/// Provider for the gRPC-based CQRS API client.
+///
+/// Uses auto-dispose to properly shut down the gRPC channel when the provider
+/// is no longer being watched. This ensures network resources are cleaned up.
+///
+/// Example usage:
+/// ```dart
+/// final grpcClient = ref.watch(grpcClientProvider);
+/// final result = await grpcClient.getDeliveryRoutes();
+/// ```
+final grpcClientProvider = Provider.autoDispose<GrpcCqrsApiClient>((ref) {
+  final authService = ref.watch(authServiceProvider);
+  final client = GrpcCqrsApiClient(
+    config: GrpcConfig.development,
+    authService: authService,
+  );
+
+  // Register disposal callback to clean up gRPC channel resources
+  ref.onDispose(() {
+    client.shutdown();
+  });
+
+  return client;
+});
+
 final isAuthenticatedProvider = FutureProvider<bool>((ref) async {
   final authService = ref.watch(authServiceProvider);
   return await authService.isAuthenticated();