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

repositories/proxy_repo.py

@@ -23,6 +23,18 @@ def _to_datetime(value: Union[str, datetime, None]) -> Optional[datetime]:
     return None
 
 
+def _row_to_proxy(row: Tuple) -> Proxy:
+    return Proxy(
+        ip=row[0],
+        port=row[1],
+        protocol=row[2],
+        score=row[3],
+        response_time_ms=row[4],
+        last_check=_to_datetime(row[5]),
+        created_at=_to_datetime(row[6]),
+    )
+
+
 class ProxyRepository:
     """代理 Repository"""
 
@@ -125,15 +137,7 @@ class ProxyRepository:
         ) as cursor:
             row = await cursor.fetchone()
             if row:
-                return Proxy(
-                    ip=row[0],
-                    port=row[1],
-                    protocol=row[2],
-                    score=row[3],
-                    response_time_ms=row[4],
-                    last_check=_to_datetime(row[5]),
-                    created_at=_to_datetime(row[6]),
-                )
+                return _row_to_proxy(row)
             return None
 
     @staticmethod
@@ -143,15 +147,7 @@ class ProxyRepository:
         ) as cursor:
             row = await cursor.fetchone()
             if row:
-                return Proxy(
-                    ip=row[0],
-                    port=row[1],
-                    protocol=row[2],
-                    score=row[3],
-                    response_time_ms=row[4],
-                    last_check=_to_datetime(row[5]),
-                    created_at=_to_datetime(row[6]),
-                )
+                return _row_to_proxy(row)
             return None
 
     @staticmethod
@@ -170,18 +166,7 @@ class ProxyRepository:
 
         async with db.execute(query, params) as cursor:
             rows = await cursor.fetchall()
-            return [
-                Proxy(
-                    ip=row[0],
-                    port=row[1],
-                    protocol=row[2],
-                    score=row[3],
-                    response_time_ms=row[4],
-                    last_check=_to_datetime(row[5]),
-                    created_at=_to_datetime(row[6]),
-                )
-                for row in rows
-            ]
+            return [_row_to_proxy(row) for row in rows]
 
     @staticmethod
     async def list_paginated(
@@ -223,18 +208,7 @@ class ProxyRepository:
         params.extend([page_size, offset])
         async with db.execute(data_query, params) as cursor:
             rows = await cursor.fetchall()
-            proxies = [
-                Proxy(
-                    ip=row[0],
-                    port=row[1],
-                    protocol=row[2],
-                    score=row[3],
-                    response_time_ms=row[4],
-                    last_check=_to_datetime(row[5]),
-                    created_at=_to_datetime(row[6]),
-                )
-                for row in rows
-            ]
+            proxies = [_row_to_proxy(row) for row in rows]
         return proxies, total
 
     @staticmethod