feat: SQLite persistence, non-blocking inference, modular frontend

Backend:
- Persist alert events and robot delivery counters in SQLite (data/app.db,
  YOLO_DB_PATH override); EventStore keeps its interface, DeliveryStatsStore
  uses read/write-through UPSERT; in-memory fallback remains for standalone
  AlertManager use
- Serve /api/detect from a sync endpoint and serialize YOLO inference with a
  lock, so concurrent requests no longer block the event loop
- Unify single-image and session detection: requests without session_id
  share the fixed single-image session and run full frame confirmation
- Store UTC Z-suffixed timestamps for sortable string comparison; close
  executor and database on shutdown via FastAPI lifespan

Frontend:
- Split app.js into ES modules (main.js + modules/{dom,api,ui,charts,store}
  + views/{dashboard,inspection,events,robots,robotCards}), no build step
- Escape all server data interpolated into innerHTML; guard missing
  event.classes; replace lazy element ID list with memoized qs()
- Remove hardcoded fake stats (trend badge, device donut segment)

Docs:
- Rewrite README: accurate weight policy (only trained best.pt committed,
  no Git LFS), SQLite persistence, single-worker note, data asset inventory
- Align models/pretrained/README.md with actual files; add YOLO_DB_PATH to
  .env.example; add persistence unit tests; ruff clean

frontend/views/robots.js

@@ -0,0 +1,41 @@
+import { qs } from "../modules/dom.js";
+import { apiFetch } from "../modules/api.js";
+import { showToast, setServiceStatus } from "../modules/ui.js";
+import { renderRobots } from "./robotCards.js";
+import { store } from "../modules/store.js";
+import { loadDashboard } from "./dashboard.js";
+
+export async function loadRobots() {
+  try {
+    const result = await apiFetch("/api/robots");
+    renderRobots(result, store.dashboardData?.detection);
+    setServiceStatus(true);
+  } catch (error) {
+    setServiceStatus(false);
+    showToast(`无法读取机器人状态：${error.message}`, "error");
+  }
+}
+
+export async function testRobot(channel, button) {
+  const originalText = button.textContent;
+  button.disabled = true;
+  button.textContent = "正在发送";
+  try {
+    const result = await apiFetch(`/api/robots/${encodeURIComponent(channel)}/test`, { method: "POST" });
+    showToast(`${result.robot.name}测试消息发送成功`, "success");
+    await Promise.all([loadRobots(), loadDashboard()]);
+  } catch (error) {
+    showToast(`测试消息发送失败：${error.message}`, "error");
+  } finally {
+    button.disabled = false;
+    button.textContent = originalText;
+  }
+}
+
+export function initRobots() {
+  qs("#refreshRobotsButton").addEventListener("click", loadRobots);
+  qs("#robotCardGrid").addEventListener("click", (event) => {
+    const button = event.target.closest("[data-test-robot]");
+    if (button) testRobot(button.dataset.testRobot, button);
+  });
+}