fix+build(client/windows): 复查修缮——一键构建脚本 + 修 README dart-define 漏项 + 清 lint

- 新增 client/windows/build.ps1：拉内核→带 --dart-define 构建→出安装包一键串联，
  规避 Release 漏 --dart-define 导致默认连 localhost、登录「网络请求失败」的坑。
- README：Release 命令补回 --dart-define 并加显式警告，指向一键脚本。
- 清 4 个 lint warning：desktop_vpn_bridge 多余 cast→pattern match、去多余非空断言；
  nav_sidebar 删未用 import；vpn_bridge_mock 加 killSwitchEnabled getter。
- 同步 window_manager/tray_manager/screen_retriever 插件注册生成文件(win+macos)。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -7,10 +7,16 @@ import Foundation
 
 import flutter_secure_storage_macos
 import package_info_plus
+import screen_retriever_macos
 import shared_preferences_foundation
+import tray_manager
+import window_manager
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
   FlutterSecureStoragePlugin.register(with: registry.registrar(forPlugin: "FlutterSecureStoragePlugin"))
   FPPPackageInfoPlusPlugin.register(with: registry.registrar(forPlugin: "FPPPackageInfoPlusPlugin"))
+  ScreenRetrieverMacosPlugin.register(with: registry.registrar(forPlugin: "ScreenRetrieverMacosPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
+  TrayManagerPlugin.register(with: registry.registrar(forPlugin: "TrayManagerPlugin"))
+  WindowManagerPlugin.register(with: registry.registrar(forPlugin: "WindowManagerPlugin"))
 }