feat: add usePWAUpdate composable and hook up in main.ts

- Add usePWAUpdate composable (singleton SW registration, periodic
  update checks, autoUpdate support)
- Call usePWAUpdate({ autoUpdate: true }) in main.ts
- Import style.css as JS side-effect in main.ts

Assisted-by: Zed:claude-sonnet-4-6

Author: Flowm

src/composables/usePWAUpdate.ts

@@ -0,0 +1,55 @@
+import { registerSW } from "virtual:pwa-register";
+import { ref } from "vue";
+
+interface UsePWAUpdateOptions {
+  /** Whether to automatically reload the app when a new version is detected. @default false */
+  autoUpdate?: boolean;
+  /** Interval in seconds to check for updates. Set to 0 to disable. @default 86400 (24 hours) */
+  updateInterval?: number;
+}
+
+// Singleton state — shared across all callers
+const needRefresh = ref(false);
+const offlineReady = ref(false);
+let updateSW: ((reloadPage?: boolean) => Promise<void>) | undefined;
+let registered = false;
+let intervalId: ReturnType<typeof setInterval> | undefined;
+
+export function usePWAUpdate(options: UsePWAUpdateOptions = {}) {
+  const { autoUpdate = false, updateInterval = 60 * 60 * 24 } = options;
+
+  const updateApp = async () => {
+    if (updateSW) {
+      try {
+        await updateSW(true);
+        needRefresh.value = false;
+      } catch (error) {
+        console.error("PWA: Failed to update app:", error);
+      }
+    }
+  };
+
+  if (!registered) {
+    registered = true;
+    updateSW = registerSW({
+      immediate: true,
+      onNeedRefresh() {
+        needRefresh.value = true;
+        if (autoUpdate) updateApp();
+      },
+      onOfflineReady() {
+        offlineReady.value = true;
+      },
+      onRegistered(registration) {
+        if (registration && updateInterval > 0 && !intervalId) {
+          intervalId = setInterval(() => registration.update(), updateInterval * 1000);
+        }
+      },
+      onRegisterError(error) {
+        console.error("PWA: Service worker registration error:", error);
+      },
+    });
+  }
+
+  return { needRefresh, offlineReady, updateApp };
+}

src/main.ts

@@ -1,9 +1,13 @@
 import { createApp } from "vue";
 
+import "./style.css";
 import App from "./App.vue";
+import { usePWAUpdate } from "./composables/usePWAUpdate";
 import { setupECharts } from "./echartsSetup";
 import { router } from "./router";
 
+usePWAUpdate({ autoUpdate: true });
+
 setupECharts();
 
 createApp(App).use(router).mount("#app");