fix: update development environment language setting to English

- Change VITE_APP_LANG from zh-cn to en in .env.development for consistency in language configuration during development

.env.development

@@ -4,7 +4,7 @@ NODE_ENV=development
 # 应用标题
 VITE_APP_TITLE=摄像头管理系统
 
-VITE_APP_LANG=zh-cn
+VITE_APP_LANG=en
 
 # API 基础路径 (通过 Vite proxy 转发到 https://tg-live-game.pwtk.cc)
 VITE_APP_BASE_API=/api