feat(app): offline-кэш на остальных экранах — фаза 5

accounts, cashflow, categories, goals, income, portfolio (+instrument),
rebalance, tax, rules переведены на Cached<T> по контракту
docs/ai/offline-cache.md. Общие/второстепенные селекторы (scopesProvider,
categoriesListProvider и т.п.) оставлены как есть — не основной контент
экрана. sync_page.dart и settings_page.dart не тронуты (первый — заменён
health-page отдельно, второй — чистые действия без списка для баннера).

app/lib/features/income/income_page.dart

@@ -1,7 +1,9 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
+import '../../core/cache/cached.dart';
 import '../../core/widgets/scope_selector.dart';
+import '../../core/widgets/stale_banner.dart';
 import 'calendar_tab.dart';
 import 'forecast_tab.dart';
 import 'history_tab.dart';
@@ -9,11 +11,21 @@ import 'providers.dart';
 
 /// Доходы: the dividend/coupon calendar, the paid history and the forecast — three views of
 /// one question, so three tabs of one screen rather than three navigation destinations.
+///
+/// One offline banner covers all three tabs (`docs/ai/offline-cache.md`): they share a
+/// scope and `TabBarView` builds all of them eagerly anyway, so watching all three
+/// providers here to compute it costs nothing extra.
 class IncomePage extends ConsumerWidget {
   const IncomePage({super.key});
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {
+    final stale = oldestFetch([
+      ref.watch(incomeCalendarProvider).valueOrNull?.fetchedAt,
+      ref.watch(incomeHistoryProvider).valueOrNull?.fetchedAt,
+      ref.watch(incomeForecastProvider).valueOrNull?.fetchedAt,
+    ]);
+
     return DefaultTabController(
       length: 3,
       child: Scaffold(
@@ -31,8 +43,19 @@ class IncomePage extends ConsumerWidget {
             tabs: [Tab(text: 'Календарь'), Tab(text: 'История'), Tab(text: 'Прогноз')],
           ),
         ),
-        body: const TabBarView(
-          children: [IncomeCalendarTab(), IncomeHistoryTab(), IncomeForecastTab()],
+        body: Column(
+          children: [
+            if (stale != null)
+              Padding(
+                padding: const EdgeInsets.fromLTRB(16, 12, 16, 0),
+                child: StaleBanner(fetchedAt: stale),
+              ),
+            const Expanded(
+              child: TabBarView(
+                children: [IncomeCalendarTab(), IncomeHistoryTab(), IncomeForecastTab()],
+              ),
+            ),
+          ],
         ),
       ),
     );