refine nginx caching strategy and add service worker update prompt with periodic checks

frontend/src/components/ui/UpdatePrompt.tsx

@@ -0,0 +1,55 @@
+import { useRegisterSW } from 'virtual:pwa-register/react';
+import { RefreshCw } from 'lucide-react';
+import { Button } from './Button';
+
+// Check for SW updates every hour and on tab focus/visibility change
+const UPDATE_INTERVAL_MS = 60 * 60 * 1000;
+
+export function UpdatePrompt() {
+  const {
+    needRefresh: [needRefresh],
+    updateServiceWorker,
+  } = useRegisterSW({
+    onRegisteredSW(_swUrl, registration) {
+      if (!registration) return;
+
+      const checkForUpdate = async () => {
+        if (registration.installing || !navigator) return;
+        if ('connection' in navigator && !navigator.onLine) return;
+        try {
+          await registration.update();
+        } catch {
+          // network error — ignore, will retry
+        }
+      };
+
+      setInterval(checkForUpdate, UPDATE_INTERVAL_MS);
+
+      const onVisible = () => {
+        if (document.visibilityState === 'visible') checkForUpdate();
+      };
+      document.addEventListener('visibilitychange', onVisible);
+      window.addEventListener('focus', checkForUpdate);
+    },
+  });
+
+  if (!needRefresh) return null;
+
+  return (
+    <div className="fixed top-0 inset-x-0 z-[60] bg-[#1B263B] text-white shadow-lg">
+      <div className="max-w-7xl mx-auto px-4 py-2 flex items-center justify-between gap-3">
+        <div className="flex items-center gap-2 text-sm">
+          <RefreshCw size={16} className="shrink-0" />
+          <span>Доступна новая версия приложения</span>
+        </div>
+        <Button
+          size="sm"
+          onClick={() => updateServiceWorker(true)}
+          className="bg-white text-[#1B263B] hover:bg-white/90"
+        >
+          Обновить
+        </Button>
+      </div>
+    </div>
+  );
+}