feat(client): 网络恢复自动刷新 + 离线嗅探 + 连通性感知登录

网络嗅探与自动恢复：
- ConnectivityNotifier：在线时 30s 检测，离线时切换为 1min 嗅探
- 新增 networkRecoveryCountProvider：网络恢复时自增，各数据 provider
  通过 ref.watch 实现自动重新加载
- inventory/product/stock_in/stock_out/partner provider 均已接入

FutureBuilder 类屏幕：
- finance_screen + batch_tracking_screen 通过 ref.listen 监听恢复事件

修复问题 1：API 超时 10s/30s → 5s/15s，减少无网络时等待
修复问题 2：offline banner 文字由"写操作已禁用"改为实际行为描述

连通性感知：
- app 启动时（_AppBootstrap）立即 forceCheck，路由跳转前状态已就绪
- 登录页：watch connectivityProvider，离线时显示警告 banner
- 登录按钮：离线状态下直接提示，不等待超时

测试：
- login_screen_test + login_flow_test 通过 ConnectivityNotifier(skipInit: true)
  覆盖 provider，避免测试环境中 pending HTTP timer

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/screens/inventory/batch_tracking_screen.dart

@@ -5,6 +5,7 @@ import '../../models/inventory.dart';
 import '../../providers/inventory_provider.dart';
 import '../../widgets/data_table_card.dart';
 import '../../widgets/multi_select_dropdown.dart' show ColDef, ColumnToggleButton, FilterableColumnHeader;
+import '../../providers/connectivity_provider.dart';
 
 class BatchTrackingScreen extends ConsumerStatefulWidget {
   const BatchTrackingScreen({super.key});
@@ -77,6 +78,9 @@ class _BatchTrackingScreenState extends ConsumerState<BatchTrackingScreen> {
 
   @override
   Widget build(BuildContext context) {
+    // 网络恢复时自动刷新
+    ref.listen(networkRecoveryCountProvider, (_, __) => _refetch());
+
     return FutureBuilder<List<ProductTrackingRecord>>(
       future: _future,
       builder: (context, snap) {