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

frontend/src/api/index.js

@@ -43,11 +43,8 @@ api.interceptors.response.use(
   }
 )
 
-/**
- * 清理请求参数，移除 null/undefined/空字符串
- * @param {object} params
- * @returns {object}
- */
+// ==================== API 模块 ====================
+
 function cleanParams(params) {
   const cleaned = {}
   Object.keys(params).forEach((key) => {
@@ -59,52 +56,20 @@ function cleanParams(params) {
   return cleaned
 }
 
-/**
- * 生成请求配置，支持 AbortSignal
- * @param {AbortSignal} [signal]
- * @returns {object}
- */
-function createRequestConfig(signal) {
-  return signal ? { signal } : {}
-}
-
-// ==================== API 模块 ====================
-
 export const statsAPI = {
-  /** @returns {Promise<import('./types').ApiResponse<import('./types').StatsData>>} */
-  getStats: () => api.get('/api/stats')
+  getStats: () => api.get('/api/proxies/stats')
 }
 
 export const proxiesAPI = {
-  /**
-   * @param {object} params
-   * @param {AbortSignal} [signal]
-   * @returns {Promise<import('./types').ApiResponse<import('./types').ProxyListData>>}
-   */
   getProxies: (params, signal) => 
-    api.post('/api/proxies', cleanParams(params), createRequestConfig(signal)),
+    api.post('/api/proxies', cleanParams(params), signal ? { signal } : {}),
   
-  /**
-   * @param {string} ip
-   * @param {number|string} port
-   * @returns {Promise<import('./types').ApiResponse<any>>}
-   */
   deleteProxy: (ip, port) => api.delete(`/api/proxies/${ip}/${port}`),
   
-  /**
-   * @param {Array<[string, number|string]>} proxies
-   * @returns {Promise<import('./types').ApiResponse<{deleted_count: number}>>}
-   */
   batchDeleteProxies: (proxies) => api.post('/api/proxies/batch-delete', { proxies }),
   
-  /** @returns {Promise<import('./types').ApiResponse<{deleted_count: number}>>} */
   cleanInvalidProxies: () => api.delete('/api/proxies/clean-invalid'),
   
-  /**
-   * @param {string} format
-   * @param {string|null} protocol
-   * @returns {Promise<Blob>}
-   */
   exportProxies: (format, protocol) => api.get(`/api/proxies/export/${format}`, {
     params: protocol ? { protocol } : {},
     responseType: 'blob'
@@ -112,48 +77,21 @@ export const proxiesAPI = {
 }
 
 export const pluginsAPI = {
-  /** @returns {Promise<import('./types').ApiResponse<{plugins: import('./types').Plugin[] }>>} */
   getPlugins: () => api.get('/api/plugins'),
-  
-  /**
-   * @param {string|number} pluginId
-   * @param {boolean} enabled
-   * @returns {Promise<import('./types').ApiResponse<any>>}
-   */
   togglePlugin: (pluginId, enabled) => api.put(`/api/plugins/${pluginId}/toggle`, { enabled }),
-  
-  /**
-   * @param {string|number} pluginId
-   * @returns {Promise<import('./types').ApiResponse<any>>}
-   */
   crawlPlugin: (pluginId) => api.post(`/api/plugins/${pluginId}/crawl`),
-  
-  /** @returns {Promise<import('./types').ApiResponse<any>>} */
   crawlAll: () => api.post('/api/plugins/crawl-all')
 }
 
 export const schedulerAPI = {
-  /** @returns {Promise<import('./types').ApiResponse<{running: boolean}>>} */
   start: () => api.post('/api/scheduler/start'),
-  
-  /** @returns {Promise<import('./types').ApiResponse<{running: boolean}>>} */
   stop: () => api.post('/api/scheduler/stop'),
-  
-  /** @returns {Promise<import('./types').ApiResponse<{started: boolean}>>} */
   validateNow: () => api.post('/api/scheduler/validate-now'),
-  
-  /** @returns {Promise<import('./types').ApiResponse<{running: boolean, interval_minutes: number}>>} */
   getStatus: () => api.get('/api/scheduler/status')
 }
 
 export const settingsAPI = {
-  /** @returns {Promise<import('./types').ApiResponse<import('./types').SettingsData>>} */
   getSettings: () => api.get('/api/settings'),
-  
-  /**
-   * @param {object} data
-   * @returns {Promise<import('./types').ApiResponse<any>>}
-   */
   saveSettings: (data) => api.post('/api/settings', data)
 }