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/widgets/connection_status_banner.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+import 'package:provider/provider.dart';
+
+import '../services/web_socket_service.dart';
+
+class ConnectionStatusBanner extends StatelessWidget {
+  const ConnectionStatusBanner({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final webSocketService = context.read<WebSocketService>();
+
+    return StreamBuilder<SocketConnectionStatus>(
+      stream: webSocketService.connectionState,
+      initialData: webSocketService.connectionStatus,
+      builder: (context, snapshot) {
+        final connectionStatus =
+            snapshot.data ?? SocketConnectionStatus.disconnected;
+        final isVisible = connectionStatus != SocketConnectionStatus.connected;
+        final isConnecting =
+            connectionStatus == SocketConnectionStatus.connecting;
+
+        return AnimatedContainer(
+          duration: const Duration(milliseconds: 250),
+          curve: Curves.easeInOut,
+          height: isVisible ? 52 : 0,
+          color:
+              isConnecting ? Colors.amber.shade700 : Colors.redAccent.shade700,
+          child: isVisible
+              ? SafeArea(
+                  bottom: false,
+                  child: Padding(
+                    padding: const EdgeInsets.symmetric(
+                      horizontal: 16,
+                      vertical: 10,
+                    ),
+                    child: Row(
+                      children: [
+                        Expanded(
+                          child: Text(
+                            isConnecting
+                                ? '正在重连...(第${webSocketService.retryCount.clamp(1, 999)}次)'
+                                : '连接断开',
+                            style: Theme.of(context)
+                                .textTheme
+                                .bodyMedium
+                                ?.copyWith(
+                                  color: Colors.black,
+                                  fontWeight: FontWeight.w600,
+                                ),
+                          ),
+                        ),
+                        if (!isConnecting)
+                          TextButton(
+                            onPressed: () {
+                              webSocketService.manualReconnect();
+                            },
+                            style: TextButton.styleFrom(
+                              foregroundColor: Colors.white,
+                              backgroundColor: Colors.black26,
+                              padding: const EdgeInsets.symmetric(
+                                horizontal: 12,
+                                vertical: 8,
+                              ),
+                            ),
+                            child: const Text('重试'),
+                          ),
+                      ],
+                    ),
+                  ),
+                )
+              : null,
+        );
+      },
+    );
+  }
+}