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/date.js

@@ -0,0 +1,24 @@
+function currentDateString(timeZone) {
+  const formatter = new Intl.DateTimeFormat("en-CA", {
+    timeZone,
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+  });
+
+  return formatter.format(new Date());
+}
+
+function compactDateString(timeZone) {
+  return currentDateString(timeZone).replaceAll("-", "");
+}
+
+function parseDateOnlyString(value) {
+  return new Date(`${value}T00:00:00.000Z`);
+}
+
+module.exports = {
+  compactDateString,
+  currentDateString,
+  parseDateOnlyString,
+};