chore(config): 新增 WebRTC 信令地址环境变量，放宽 pnpm 版本约束并移除 overrides

types/env.d.ts

@@ -7,6 +7,7 @@ interface ImportMetaEnv {
   readonly VITE_APP_PORT: string;
   readonly VITE_APP_BASE_API: string;
   readonly VITE_APP_API_URL: string;
+  readonly VITE_WEBRTC_SIGNAL_URL?: string;
   readonly VITE_APP_TITLE?: string;
   readonly VITE_APP_TENANT_ENABLED?: string;
   readonly VITE_MOCK_DEV_SERVER: boolean;