全面清理冗余与过度分层

后端优化：
- 合并 api/routes/stats.py 到 api/routes/proxies.py，统计接口变更为 /api/proxies/stats
- 内联 services/settings_service.py：settings.py 和 scheduler.py 直接使用 SettingsRepository
- 简化 repositories/proxy_repo.py：提取 _row_to_proxy 辅助函数，消除重复构造代码
- 更新 api/lifespan.py 和 api/deps.py，移除对 settings_service 的依赖
- 从 requirements.txt 移除 websockets 依赖（已废弃的 WebSocket 功能残留）

前端适配：
- 更新 frontend/src/api/index.js：stats 接口路径同步为 /api/proxies/stats
- 清理 api/index.js 中未使用的 createRequestConfig 和多余 JSDoc 注释

脚本优化：
- 移除 script/stop.bat 末尾的 pause，避免自动化调用时挂起

api/routes/scheduler.py

@@ -1,11 +1,13 @@
 """调度器相关路由"""
 from fastapi import APIRouter, Depends
 from services.scheduler_service import SchedulerService
-from services.settings_service import SettingsService
+from repositories.settings_repo import SettingsRepository
+from core.db import get_db
 from api.deps import get_scheduler_service
 from core.log import logger
 
 router = APIRouter(prefix="/api/scheduler", tags=["scheduler"])
+settings_repo = SettingsRepository()
 
 
 def success_response(message: str, data=None):
@@ -25,11 +27,11 @@ async def start_scheduler(
             return success_response("验证调度器已在运行", {"running": True})
         await scheduler.start()
         # 持久化设置
-        settings_service = SettingsService()
-        settings = await settings_service.get_settings()
-        settings["auto_validate"] = True
-        from models.schemas import SettingsSchema
-        await settings_service.save_settings(SettingsSchema(**settings))
+        async with get_db() as db:
+            settings = await settings_repo.get_all(db)
+            settings["auto_validate"] = True
+            from models.schemas import SettingsSchema
+            await settings_repo.save(db, SettingsSchema(**settings).model_dump())
         return success_response("验证调度器已启动", {"running": True})
     except Exception as e:
         logger.error(f"Start scheduler failed: {e}")
@@ -45,11 +47,11 @@ async def stop_scheduler(
             return success_response("验证调度器未运行", {"running": False})
         await scheduler.stop()
         # 持久化设置
-        settings_service = SettingsService()
-        settings = await settings_service.get_settings()
-        settings["auto_validate"] = False
-        from models.schemas import SettingsSchema
-        await settings_service.save_settings(SettingsSchema(**settings))
+        async with get_db() as db:
+            settings = await settings_repo.get_all(db)
+            settings["auto_validate"] = False
+            from models.schemas import SettingsSchema
+            await settings_repo.save(db, SettingsSchema(**settings).model_dump())
         return success_response("验证调度器已停止", {"running": False})
     except Exception as e:
         logger.error(f"Stop scheduler failed: {e}")