refactor: 全面优化后端代码质量与架构

- app.ts 单体路由拆分为 routes/ + helpers + middleware + static 独立模块
- 类型去重：CheckFailure/CheckResult 以 shared/api.ts 为唯一源头，收紧 phase 联合类型
- es-toolkit 替换：isPlainObject/isNil/isEmptyObject/isEqual/isError/Semaphore/groupBy
- Bun 内置 API：Object.fromEntries 替代手写 headersToRecord
- bun:sqlite 规范：prepare() → query() 利用内置缓存，避免 N+1 查询
- 新增 getLatestChecksMap/allGetTargetStats 批量查询方法
- 新增 backend-code-quality/api-route-separation/batch-data-queries 规范
- 补充 openspec/config.yaml 后端开发规范与 DEVELOPMENT.md 后端开发指引

package.json

@@ -38,6 +38,7 @@
     "@tanstack/react-query": "^5.100.10",
     "@xmldom/xmldom": "^0.9.10",
     "cheerio": "^1.2.0",
+    "es-toolkit": "^1.46.1",
     "react": "^19.2.6",
     "react-dom": "^19.2.6",
     "recharts": "^3.8.1",