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/lib/features/calendar/ui/widgets/create_event_sheet.dart

@@ -638,7 +638,11 @@ class _CreateEventSheetState extends State<CreateEventSheet>
       try {
         final notificationService = sl<LocalNotificationService>();
         await notificationService.upsertEventReminder(saved);
-      } catch (_) {}
+      } catch (_) {
+        if (mounted) {
+          Toast.show(context, '提醒创建失败，请检查通知权限', type: ToastType.warning);
+        }
+      }
 
       widget.onSaved?.call();
       if (mounted) {