feat(mobile): upload queue ui and continuous capture page

Task 9 (P3 plan): queue tab replaces the stub, continuous capture page
enqueues per shot, album detail gains an upload FAB, and the upload
engine lifecycle is now bound to the login session.

- Engine scope: session account drives UploadEngine start/stop; wired
  from app boot, login success, logout, and 401 eviction. Tasks stay in
  the store across logout (accountId hard isolation).
- Queue tab: album x state x time filter bar, task rows with thumbnail,
  state chip, localized error copy, attempt count, per-row progress via
  a broadcast progress hub, state-dependent actions (re-pick retry,
  retryNow, cancel, delete), batch retry bar, 200ms-debounced live
  refresh from drift table updates.
- Capture page: camera preview via injected CaptureSource, one enqueue
  per shutter press, persistent album/category/badges overlay with a
  switch-only-affects-new-shots hint, gallery multi-pick, exit confirm
  while uploads are pending, permission-denied and init-failure views.
- POST_NOTIFICATIONS runtime permission via a small MethodChannel
  (photolive/permissions) + PermissionPlugin.kt: single runtime
  permission need, avoids permission_handler dependency; requested once
  on first enqueue, silent degradation when denied or unavailable.
- Album detail FAB: capture-and-upload / pick-from-gallery sheet.
- l10n: ~50 new keys in zh/en arbs; tests: +45 (filter matrix, engine
  scope lifecycle, permission gate, queue tab, capture page, FAB entry);
  existing page tests updated to inject session/task-store fakes.

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

apps/mobile/lib/app/app.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../core/api_client.dart';
+import '../features/uploads/engine_scope.dart';
 import '../l10n/app_localizations.dart';
 import '../pages/home_page.dart';
 import '../pages/login_page.dart';
@@ -14,12 +15,15 @@ import 'theme.dart';
 final GlobalKey<NavigatorState> rootNavigatorKey =
     GlobalKey<NavigatorState>();
 
-/// App 根组件：主题 + l10n 委托 + 命名路由 + 401 驱逐接线。
+/// App 根组件：主题 + l10n 委托 + 命名路由 + 401 驱逐接线 + 引擎生命周期。
 ///
 /// 基线路由为命名路由（/login → /home → /password-change）；随页面增长再
 /// 评估是否迁移 go_router，当前保持零额外依赖。
 /// initState 注册 [ApiClient.onUnauthorized]：任意业务端点 401（会话过期）
-/// 即清空栈回到 /login（登录/修改密码端点自身的 401 不触发，见 ApiClient）。
+/// 即清空栈回到 /login（登录/修改密码端点自身的 401 不触发，见 ApiClient），
+/// 并同步刷新会话账号（引擎 stop，任务保留库内）。
+/// build watch [uploadEngineScopeProvider]——App 存续期间引擎随登录态
+/// start/stop（Task 9 接线，见 engine_scope.dart）。
 class PhotoLiveApp extends ConsumerStatefulWidget {
   const PhotoLiveApp({super.key});
 
@@ -34,12 +38,16 @@ class _PhotoLiveAppState extends ConsumerState<PhotoLiveApp> {
     ref.read(apiClientProvider).onUnauthorized = () {
       rootNavigatorKey.currentState
           ?.pushNamedAndRemoveUntil('/login', (route) => false);
+      // 401 已清会话（ApiClient）：刷新账号观察 → 引擎 stop。
+      ref.read(sessionAccountProvider.notifier).refresh();
     };
   }
 
   @override
   Widget build(BuildContext context) {
     final locale = ref.watch(localeSettingsProvider);
+    // 引擎生命周期绑定（常驻 watch；账号在场 start / 离场 stop）。
+    ref.watch(uploadEngineScopeProvider);
     return MaterialApp(
       navigatorKey: rootNavigatorKey,
       onGenerateTitle: (context) => AppLocalizations.of(context).appName,