feat: 商业保险/员工福利独立页面+易签宝电子签署框架

- 商业保险：从社公商保中拆出为独立页面，侧边栏新增「福利保障」分组
- 员工福利：新建完整模块（方案管理+批量参保+员工汇总），Prisma模型+后端路由+前端页面
- 电子签署：搭建易签宝对接框架（ESignRecord模型+创建/查询/取消/回调接口+前端签署管理页面）
- 侧边栏新增「福利保障」分组：商业保险、员工福利、电子签署
- Prisma schema 新增6个模型：CommercialInsurancePlan/Enrollment, EmployeeBenefitPlan/Enrollment, ESignRecord

backend/src/app.ts

@@ -66,6 +66,9 @@ import companyFileRoutes from './routes/company-file.routes'
 import acceptanceTestRoutes from './routes/acceptance-test.routes'
 import leaveRoutes from './routes/leave.routes'
 import salaryRoutes from './routes/salary.routes'
+import commercialInsuranceRoutes from './routes/commercial-insurance.routes'
+import benefitRoutes from './routes/benefit.routes'
+import esignRoutes from './routes/esign.routes'
 app.use('/api/v1/auth', authRoutes)
 app.use('/api/v1/dashboard', dashboardRoutes)
 app.use('/api/v1/employees', employeeRoutes)
@@ -95,6 +98,9 @@ app.use('/api/v1/company-files', companyFileRoutes)
 app.use('/api/v1/acceptance-tests', acceptanceTestRoutes)
 app.use('/api/v1/leaves', leaveRoutes)
 app.use('/api/v1/salary', salaryRoutes)
+app.use('/api/v1/commercial-insurance', commercialInsuranceRoutes)
+app.use('/api/v1/benefits', benefitRoutes)
+app.use('/api/v1/esign', esignRoutes)
 
 app.use(errorHandler)