refactor(server): 用已装库替换手写工具

- uuid v7 替换手写 RFC9562 实现（uuid@11.1.1 转为直接依赖）
- node:timers/promises setTimeout 替换两处手写 sleep（钉钉限流、AI 上游重试退避）
- dayjs 替换 4 处零散 Date 格式化（imports/expenses/occupancies 导入模板、档案报告日期）

package-lock.json

@@ -125,7 +125,8 @@
         "pino": "^10.3.1",
         "reflect-metadata": "^0.2.2",
         "rxjs": "^7.8.1",
-        "typeorm": "^0.3.31"
+        "typeorm": "^0.3.31",
+        "uuid": "^11.1.1"
       },
       "devDependencies": {
         "@eslint/js": "^9.18.0",