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/pages/login_page.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../core/api_client.dart';
 import '../core/app_exception.dart';
 import '../core/error_l10n.dart';
+import '../features/uploads/engine_scope.dart';
 import '../l10n/app_localizations.dart';
 
 /// 登录页（P3 计划 Task 3）。
@@ -44,6 +45,8 @@ class _LoginPageState extends ConsumerState<LoginPage> {
             _accountController.text.trim(),
             _passwordController.text,
           );
+      // 登录成功：刷新会话账号 → 引擎以新账号 scope start（Task 9 接线）。
+      await ref.read(sessionAccountProvider.notifier).refresh();
       navigator.pushReplacementNamed('/home');
     } on AppException catch (error) {
       // 429（AUTH_RATE_LIMITED）等文案经错误码映射；登录页的