refactor: 移除 LiteLLM proxy 架构，后端直连 Provider API

- 移除 backend/scripts/build_litellm_proxy_config.py
- 简化 LiteLLMService，移除 run_completion_with_cost 方法
- AgentScopeRunner 改为从 LlmFactory 获取 api_base 和 api_key
- 部署配置移除 litellm/litellm-config-job 服务
- Flutter 新增 AuthBootScreen 引导页
- Android 添加通知权限 (POST_NOTIFICATIONS, RECEIVE_BOOT_COMPLETED, SCHEDULE_EXACT_ALARM)
- 优化 LocalNotificationService 调度失败 fallback
- 更新 manifest.json (version 3)

apps/android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
     <uses-permission android:name="android.permission.RECORD_AUDIO" />
     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" android:maxSdkVersion="32" />