refactor: 后端架构加固 — 泛型化、批量查询、bootstrap 统一、路径修复与 pageSize 上限

- CheckerDefinition 泛型化，HTTP/Command checker 移除 resolved target 断言
- 新增 ProbeStore.getAllRecentSamples 消除 targets 路由 N+1 查询
- 统一 getAllTargetStats 与 getTargetStats 的 availability 精度
- Engine rejected 结果写入 internal error 记录，提升可观测性
- 新增 bootstrap.ts 统一 dev/production 启动序列
- dataDir 相对路径改为基于配置文件目录解析
- validatePagination 增加 pageSize 上限 200 校验
- 修复 ErrorBoundary override 标记
- 更新 README/DEVELOPMENT 文档，新增完整测试覆盖

src/server/checker/runner/http/execute.ts

@@ -1,7 +1,7 @@
 import { isError } from "es-toolkit";
 
-import type { CheckResult, RawTargetConfig, ResolvedTargetBase } from "../../types";
-import type { Checker, CheckerContext, CheckerValidationInput, ResolveContext } from "../types";
+import type { CheckResult, RawTargetConfig } from "../../types";
+import type { CheckerContext, CheckerDefinition, CheckerValidationInput, ResolveContext } from "../types";
 import type { HttpExpectConfig, HttpTargetConfig, ResolvedHttpTarget } from "./types";
 
 import { checkDuration } from "../../expect/duration";
@@ -16,15 +16,14 @@ const CHARSET_RE = /charset="?([^";\s]+)"?/i;
 const REDIRECT_STATUSES = new Set([301, 302, 303, 307, 308]);
 const SENSITIVE_HEADERS = new Set(["authorization", "cookie"]);
 
-export class HttpChecker implements Checker {
+export class HttpChecker implements CheckerDefinition<ResolvedHttpTarget> {
   readonly configKey = "http";
 
   readonly schemas = httpCheckerSchemas;
 
   readonly type = "http";
 
-  async execute(target: ResolvedTargetBase, ctx: CheckerContext): Promise<CheckResult> {
-    const t = target as ResolvedHttpTarget;
+  async execute(t: ResolvedHttpTarget, ctx: CheckerContext): Promise<CheckResult> {
     const timestamp = new Date().toISOString();
     const expect = t.expect;
     const start = performance.now();
@@ -117,7 +116,7 @@ export class HttpChecker implements Checker {
     }
   }
 
-  resolve(target: RawTargetConfig, context: ResolveContext): ResolvedTargetBase {
+  resolve(target: RawTargetConfig, context: ResolveContext): ResolvedHttpTarget {
     const t = target as RawTargetConfig & { http: HttpTargetConfig; type: "http" };
     const httpDefaults = context.defaults["http"] as
       | undefined
@@ -145,8 +144,7 @@ export class HttpChecker implements Checker {
     } satisfies ResolvedHttpTarget;
   }
 
-  serialize(target: ResolvedTargetBase): { config: string; target: string } {
-    const t = target as ResolvedHttpTarget;
+  serialize(t: ResolvedHttpTarget): { config: string; target: string } {
     return {
       config: JSON.stringify({
         body: t.http.body,