added timestamp to bloc cache, showing age in offline mode

lib/state/app/infrastructure/loadableState/loadable_state.dart

@@ -11,6 +11,7 @@ class LoadableState<TState> with _$LoadableState {
   const factory LoadableState({
     @Default(true) bool isLoading,
     @Default(null) TState? data,
+    @Default(null) int? lastFetch,
     @Default(null) void Function()? reFetch,
     @Default(null) LoadingError? error,
   }) = _LoadableState;