fix: 安全性与代码质量加固（异常保护、外键级联、竞态修复、优雅关机）

tests/server/app.test.ts

@@ -254,4 +254,33 @@ describe("API 路由", () => {
     const asset = await fetchHandler(new Request("http://localhost/assets/app.js"));
     expect(asset.status).toBe(200);
   });
+
+  test("损坏的 failure JSON 返回 null 而不崩溃", async () => {
+    const targets = store.getTargets();
+    const t1Id = targets[0]!.id;
+
+    store.insertCheckResult({
+      targetId: t1Id,
+      timestamp: "2025-06-01T00:00:00.000Z",
+      matched: false,
+      durationMs: 100,
+      statusDetail: "200 OK",
+      failure: { kind: "error", phase: "body", path: "$", message: "test" },
+    });
+
+    (store as unknown as { db: { prepare: (sql: string) => { run: (...args: unknown[]) => void } } }).db
+      .prepare("UPDATE check_results SET failure = ? WHERE target_id = ? AND timestamp = ?")
+      .run("{invalid json!!!", t1Id, "2025-06-01T00:00:00.000Z");
+
+    const from = "2025-06-01T00:00:00.000Z";
+    const to = "2025-06-01T23:59:59.999Z";
+    const response = await fetchHandler(
+      new Request(`http://localhost/api/targets/${t1Id}/history?from=${from}&to=${to}`),
+    );
+    const body = (await response.json()) as HistoryResponse;
+
+    expect(response.status).toBe(200);
+    expect(body.items).toHaveLength(1);
+    expect(body.items[0]!.failure).toBeNull();
+  });
 });