feat: 实现客服工作台功能 (Issue #54)

- 添加 CustomerServiceController 后端 API
- 实现前端客服工作台界面
- 支持水费查询（户号/手机号）
- 集成 TTS 语音查询功能
- 添加数据库表结构和示例数据
- 更新路由配置

Resolves: #54

frontend/src/api/customerService.ts

@@ -0,0 +1,41 @@
+import { request } from '@/utils/request'
+
+export interface QueryBillsParams {
+  phoneOrCustomerNo: string
+}
+
+export interface KnowledgeSearchParams {
+  keyword: string
+}
+
+export interface NoticeParams {
+  type: string
+}
+
+export interface KpiData {
+  pending_bills: number
+  pending_installs: number
+  avg_install_hours: number
+}
+
+export const serviceApi = {
+  // 水费查询
+  queryBills: (params: QueryBillsParams) => {
+    return request.get('/service/query-bills', { params })
+  },
+  
+  // 知识库搜索
+  searchKnowledge: (params: KnowledgeSearchParams) => {
+    return request.get('/service/search-knowledge', { params })
+  },
+  
+  // 获取公告
+  getNotices: (params: NoticeParams) => {
+    return request.get('/service/notices/{type}', { params })
+  },
+  
+  // 获取KPI
+  getKpi: () => {
+    return request.get('/service/kpi')
+  }
+}