refactor: 代码审查修复 — 错误边界、DRY抽取、测试修复、合规性改进

- P1: server.ts 统一错误边界 (withErrorHandler + AppError)，修复 3 个失败/卡死测试
- P2: db 层 wrap/paginateQuery 抽取，前端 handleResponse 抽取，parseIdFromUrl 抽取
- P3: middleware 验证消息中文化，Flex→Space 替换
- P0: docs/development/README.md 新增已知设计决策章节
- P3-11 setup 拆分已尝试回退（@testing-library/react preload 依赖无法拆分）
- P3-13 config 层测试从本次变更移除

src/server/routes/projects/delete.ts

@@ -3,12 +3,12 @@ import type Database from "bun:sqlite";
 import type { RuntimeMode } from "../../../shared/api";
 
 import { deleteProject } from "../../db/projects";
-import { createApiError, jsonResponse } from "../../helpers";
+import { createApiError, jsonResponse, parseIdFromUrl } from "../../helpers";
 import { validateIdParam } from "../../middleware";
 
 export function handleDeleteProject(req: Request, db: Database, mode: RuntimeMode): Response {
   const url = new URL(req.url);
-  const idStr = url.pathname.split("/")[3];
+  const idStr = parseIdFromUrl(url);
 
   const validated = validateIdParam(idStr ?? "", mode);
   if (validated instanceof Response) return validated;

src/server/routes/providers/delete.ts

@@ -4,12 +4,12 @@ import type { RuntimeMode } from "../../../shared/api";
 
 import { getModelsByProviderId } from "../../db/models";
 import { deleteProvider } from "../../db/providers";
-import { createApiError, jsonResponse } from "../../helpers";
+import { createApiError, jsonResponse, parseIdFromUrl } from "../../helpers";
 import { validateIdParam } from "../../middleware";
 
 export function handleDeleteProvider(req: Request, db: Database, mode: RuntimeMode): Response {
   const url = new URL(req.url);
-  const idStr = url.pathname.split("/")[3];
+  const idStr = parseIdFromUrl(url);
 
   const validated = validateIdParam(idStr ?? "", mode);
   if (validated instanceof Response) return validated;