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/engine.ts

@@ -0,0 +1,87 @@
+import type { CheckResult, ResolvedTarget } from "./types";
+import type { ProbeStore } from "./store";
+import { fetchTarget } from "./fetcher";
+
+export class ProbeEngine {
+  private timers: ReturnType<typeof setInterval>[] = [];
+  private store: ProbeStore;
+  private targetNameToId: Map<string, number> = new Map();
+
+  constructor(store: ProbeStore, targets: ResolvedTarget[]) {
+    this.store = store;
+    this.targets = targets;
+    this.refreshCache();
+  }
+
+  start(): void {
+    const groups = this.groupByInterval(this.targets);
+
+    for (const [intervalMs, groupTargets] of groups) {
+      void this.probeGroup(groupTargets);
+
+      const timer = setInterval(() => {
+        void this.probeGroup(groupTargets);
+      }, intervalMs);
+
+      this.timers.push(timer);
+    }
+  }
+
+  stop(): void {
+    for (const timer of this.timers) {
+      clearInterval(timer);
+    }
+    this.timers = [];
+  }
+
+  private groupByInterval(targets: ResolvedTarget[]): Map<number, ResolvedTarget[]> {
+    const groups = new Map<number, ResolvedTarget[]>();
+
+    for (const target of targets) {
+      const group = groups.get(target.intervalMs) ?? [];
+      group.push(target);
+      groups.set(target.intervalMs, group);
+    }
+
+    return groups;
+  }
+
+  private async probeGroup(targets: ResolvedTarget[]): Promise<void> {
+    const results = await Promise.allSettled(targets.map((t) => this.probeOne(t)));
+
+    for (const result of results) {
+      if (result.status === "fulfilled") {
+        this.writeResult(result.value);
+      }
+    }
+  }
+
+  private async probeOne(target: ResolvedTarget): Promise<CheckResult> {
+    return fetchTarget(target);
+  }
+
+  private writeResult(result: CheckResult): void {
+    const targetId = this.targetNameToId.get(result.targetName);
+
+    if (!targetId) return;
+
+    this.store.insertCheckResult({
+      targetId,
+      timestamp: result.timestamp,
+      success: result.success,
+      statusCode: result.statusCode,
+      latencyMs: result.latencyMs,
+      error: result.error,
+      matched: result.matched,
+    });
+  }
+
+  private refreshCache(): void {
+    this.targetNameToId.clear();
+    for (const target of this.store.getTargets()) {
+      this.targetNameToId.set(target.name, target.id);
+    }
+  }
+
+  private targets: ResolvedTarget[];
+}