feat(server): 完成 P0+P1 后端能力（工作流、RBAC、付款归档）

P0 MVP：

- 认证：login/refresh/logout/forgot/reset + tokenVersion

- RBAC：角色到权限映射 + requirePermission

- 发票池：upload/bind/signed-url + 判重（VALID_003/VALID_005）

- 报销：create/view/submit + 单号生成

- 工作流：approve + department_manager 解析

P1 扩展：

- 动作：reject/return/withdraw（含 comment）

- transfer：任务转审 + 链路上限 3

- pay：approved -> paid + 发票归档 used_complete

- 动态审批链：approval_rules 驱动

回归脚本：

- smoke-test.sh / regression-dedup.sh / regression-workflow-actions.sh

server/src/utils/audit.js

@@ -0,0 +1,17 @@
+function buildAuditLogData(request, params) {
+  const userAgent = request.headers["user-agent"];
+
+  return {
+    request_id: request.id,
+    actor_id: params.actorId,
+    action: params.action,
+    target_type: params.targetType,
+    target_id: params.targetId ?? null,
+    ip_address: request.ip,
+    user_agent: typeof userAgent === "string" ? userAgent : null,
+    extra: params.extra ?? {},
+  };
+}
+
+module.exports = { buildAuditLogData };
+