auto-claude: subtask-4-3 - Create gRPC-based deliveries provider

Add grpcDeliveriesProvider as a gRPC-based alternative to deliveriesProvider.
The new provider uses GrpcCqrsApiClient.getDeliveries() for improved
performance and type safety. Follows the existing pattern with:
- FutureProvider.family pattern for route-specific queries
- Authentication check before API calls
- Result.when() for proper error handling
- Warehouse delivery appended at the end

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

lib/providers/providers.dart

@@ -132,6 +132,47 @@ final grpcDeliveryRoutesProvider = FutureProvider<List<DeliveryRoute>>((ref) asy
   );
 });
 
+/// Provider for deliveries using gRPC.
+///
+/// This is the gRPC-based alternative to [deliveriesProvider].
+/// Uses [GrpcCqrsApiClient] for improved performance and type safety.
+/// Takes a [routeFragmentId] parameter to fetch deliveries for a specific route.
+///
+/// Example usage:
+/// ```dart
+/// final deliveries = ref.watch(grpcDeliveriesProvider(routeFragmentId));
+/// deliveries.when(
+///   data: (data) => displayDeliveries(data),
+///   loading: () => showLoading(),
+///   error: (error, stack) => showError(error),
+/// );
+/// ```
+final grpcDeliveriesProvider = FutureProvider.family<List<Delivery>, int>((ref, routeFragmentId) async {
+  final authService = ref.watch(authServiceProvider);
+  final isAuthenticated = await authService.isAuthenticated();
+
+  if (!isAuthenticated) {
+    throw Exception('User not authenticated');
+  }
+
+  final grpcClient = ref.watch(grpcClientProvider);
+  final result = await grpcClient.getDeliveries(routeFragmentId: routeFragmentId);
+
+  final deliveries = result.when(
+    success: (deliveries) => deliveries,
+    onError: (error) {
+      debugPrint('ERROR fetching deliveries for route $routeFragmentId via gRPC: ${error.message}');
+      if (error.originalException != null) {
+        debugPrint('Original exception: ${error.originalException}');
+      }
+      throw Exception(error.message);
+    },
+  );
+
+  // Always append the warehouse delivery at the end
+  return [...deliveries, Delivery.createWarehouseDelivery()];
+});
+
 final deliveriesProvider = FutureProvider.family<List<Delivery>, int>((ref, routeFragmentId) async {
   final authService = ref.watch(authServiceProvider);
   final isAuthenticated = await authService.isAuthenticated();