feat: 电子签全场景集成+场景筛选+设置开关

- ESignRecord 模型新增 scene 字段（CONTRACT/RESIGNATION/POLICY/PAYSLIP/ONBOARDING）
- Organization 模型新增3个电子签开关：esignPolicyEnabled/esignPayslipEnabled/esignOnboardingEnabled
- 设置页面企业信息新增电子签署设置区域，3个开关各自独立，缺省关闭
- 规章制度签收：开启电子签后，员工阅读确认时自动创建POLICY场景签署记录
- 工资条确认：开启电子签后，员工确认工资条时自动创建PAYSLIP场景签署记录
- 入职文件签署：开启电子签后，HR审批通过入职流程时自动创建ONBOARDING场景签署记录
- 电子签署列表增加场景筛选下拉（全部场景/劳动合同/离职协议/规章制度/工资条/入职文件）
- 管理端和员工端列表均展示场景标签（基于scene字段，替代硬编码判断）
- 合同和离职流程的esign调用已加scene参数

backend/src/routes/esign.routes.ts

@@ -12,16 +12,19 @@ const createSignSchema = z.object({
   documentTitle: z.string().min(1),
   documentContent: z.string().optional(),
   remark: z.string().optional(),
+  scene: z.string().optional(),
 })
 
 // 签署记录列表
 router.get('/', async (req: AuthRequest, res: Response, next: NextFunction) => {
   try {
     const status = req.query.status as string | undefined
+    const scene = req.query.scene as string | undefined
     const records = await prisma.eSignRecord.findMany({
       where: {
         orgId: req.user!.orgId,
         ...(status && { status }),
+        ...(scene && { scene }),
       },
       include: {
         employee: { select: { id: true, name: true, department: true, phone: true } },
@@ -56,6 +59,7 @@ router.post('/create', async (req: AuthRequest, res: Response, next: NextFunctio
         orgId: req.user!.orgId,
         contractId: data.contractId || null,
         employeeId: data.employeeId,
+        scene: data.scene || 'CONTRACT',
         documentTitle: data.documentTitle,
         documentContent: data.documentContent || null,
         // flowId: esignResult.flowId,  // TODO: 易签宝对接后启用