feat: M1.1 完成 + M1.2 启动 — 全量更新

M1.1 收尾:
- 24项 P0/P1/P2 bug 修复 (Rust 107 tests + Flutter 15 tests)
- Flutter App v0.3: cupertino_icons 修复, 单元测试, 调试面板, APK 52.6MB
- 示例插件完善: manifest.json + 请求/响应示范 + 7个测试
- API 文档重写 (以 routes.rs 为唯一权威)
- MILESTONES.md 更新至 100%

M1.2 启动:
- P0: 插件管理 API 闭环 (handle_manager_message Custom 分支 + broadcast_plugin_states)
- ServiceManager 集成测试 8/8 (tests/m1_2_service_manager.rs)
- M1.2 测试计划 (docs/M1.2_TEST_PLAN.md, 18个E2E场景)
- 动态插件系统: auto_rollback + version_manager GC + 路径穿越防护

总计: Rust 115/115 测试, Flutter 15/15 测试, 零 warning

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

clients/flutter/lib/screens/app_shell.dart

@@ -1,6 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 
+import '../widgets/connection_status_banner.dart';
+
 class AppShell extends StatelessWidget {
   const AppShell({required this.navigationShell, super.key});
 
@@ -9,7 +11,12 @@ class AppShell extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      body: navigationShell,
+      body: Column(
+        children: [
+          const ConnectionStatusBanner(),
+          Expanded(child: navigationShell),
+        ],
+      ),
       bottomNavigationBar: NavigationBar(
         selectedIndex: navigationShell.currentIndex,
         onDestinationSelected: (index) {
@@ -44,6 +51,11 @@ class AppShell extends StatelessWidget {
             selectedIcon: Icon(Icons.settings),
             label: '设置',
           ),
+          NavigationDestination(
+            icon: Icon(Icons.bug_report_outlined),
+            selectedIcon: Icon(Icons.bug_report),
+            label: '调试',
+          ),
         ],
       ),
     );