feat: 将 demo 项目转化为 HTTP 拨测监控工具

新增 YAML 配置解析（Bun 内置 YAML）、SQLite 数据存储（bun:sqlite）、按 interval 分组并发拨测引擎、REST API（/api/summary、/api/targets、/api/targets/:id/history、/api/targets/:id/trend）、React 前端 Dashboard（统计卡片、目标表格、可展开详情面板、recharts 趋势图）。CLI 简化为仅接受配置文件路径。移除 /api/demo 路由和相关 demo 代码。保留 /health、静态资源服务和 SPA fallback。

src/server/checker/fetcher.ts

@@ -0,0 +1,65 @@
+import type { CheckResult, ExpectConfig, ResolvedTarget } from "./types";
+
+export async function fetchTarget(target: ResolvedTarget): Promise<CheckResult> {
+  const timestamp = new Date().toISOString();
+  const controller = new AbortController();
+  const timeoutId = setTimeout(() => controller.abort(), target.timeoutMs);
+
+  try {
+    const start = performance.now();
+
+    const response = await fetch(target.url, {
+      method: target.method,
+      headers: target.headers,
+      body: target.method !== "GET" && target.method !== "HEAD" ? target.body : undefined,
+      signal: controller.signal,
+    });
+
+    const latencyMs = Math.round(performance.now() - start);
+    const body = await response.text();
+
+    const matched = checkExpect(response.status, body, latencyMs, target.expect);
+
+    return {
+      targetName: target.name,
+      timestamp,
+      success: true,
+      statusCode: response.status,
+      latencyMs,
+      error: null,
+      matched,
+    };
+  } catch (error) {
+    const isTimeout = error instanceof DOMException && error.name === "AbortError";
+
+    return {
+      targetName: target.name,
+      timestamp,
+      success: false,
+      statusCode: null,
+      latencyMs: null,
+      error: isTimeout ? `请求超时 (${target.timeoutMs}ms)` : (error instanceof Error ? error.message : String(error)),
+      matched: false,
+    };
+  } finally {
+    clearTimeout(timeoutId);
+  }
+}
+
+export function checkExpect(statusCode: number, body: string, latencyMs: number, expect?: ExpectConfig): boolean {
+  if (!expect) return true;
+
+  if (expect.status && !expect.status.includes(statusCode)) {
+    return false;
+  }
+
+  if (expect.bodyContains && !body.includes(expect.bodyContains)) {
+    return false;
+  }
+
+  if (expect.maxLatencyMs !== undefined && latencyMs > expect.maxLatencyMs) {
+    return false;
+  }
+
+  return true;
+}