feat: Add push notifications for background friend pings

- Auto-subscribe to push notifications when location sharing starts
- Use C3NavEmbed (iframe) for faster indoor map loading
- Set event to 39c3 for current congress
- Increase c3nav API cache to 1 hour with stale-while-revalidate
- Add strong vibration pattern and sound for notifications

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

public/sw.js

@@ -103,9 +103,14 @@ self.addEventListener('push', (event) => {
     badge: data.badge || '/icon-192.png',
     tag: data.tag || 'rmaps-notification',
     data: data.data || {},
-    vibrate: [100, 50, 100],
+    // Strong vibration pattern: buzz-pause-buzz-pause-long buzz
+    vibrate: [200, 100, 200, 100, 400],
     actions: data.actions || [],
     requireInteraction: data.requireInteraction || false,
+    // Use default system notification sound
+    silent: false,
+    // Renotify even if same tag (so user hears it again)
+    renotify: true,
   };
 
   event.waitUntil(

src/app/[slug]/page.tsx

@@ -6,6 +6,7 @@ import dynamic from 'next/dynamic';
 import { useRoom } from '@/hooks/useRoom';
 import { useLocationSharing } from '@/hooks/useLocationSharing';
 import { useServiceWorkerMessages } from '@/hooks/useServiceWorkerMessages';
+import { usePushNotifications } from '@/hooks/usePushNotifications';
 import ParticipantList from '@/components/room/ParticipantList';
 import RoomHeader from '@/components/room/RoomHeader';
 import ShareModal from '@/components/room/ShareModal';
@@ -140,6 +141,23 @@ export default function RoomPage() {
     },
   });
 
+  // Push notifications for background pings
+  const syncUrl = process.env.NEXT_PUBLIC_SYNC_URL;
+  const { subscribe: subscribePush, isSubscribed: isPushSubscribed } = usePushNotifications({
+    syncUrl,
+    roomSlug: slug,
+  });
+
+  // Auto-subscribe to push when location sharing starts
+  useEffect(() => {
+    if (isSharing && !isPushSubscribed && syncUrl) {
+      console.log('Auto-subscribing to push notifications for background pings');
+      subscribePush().catch((err) => {
+        console.warn('Push subscription failed (user may have denied):', err.message);
+      });
+    }
+  }, [isSharing, isPushSubscribed, subscribePush, syncUrl]);
+
   // Restore last known location immediately when connected
   const hasRestoredLocationRef = useRef(false);
   useEffect(() => {

src/app/api/c3nav/[event]/route.ts

@@ -128,7 +128,7 @@ export async function GET(request: NextRequest, { params }: RouteParams) {
     return NextResponse.json(data, {
       status: 200,
       headers: {
-        'Cache-Control': 'public, max-age=300', // Cache for 5 minutes
+        'Cache-Control': 'public, max-age=3600, stale-while-revalidate=86400', // Cache 1 hour, stale 24h
         'Access-Control-Allow-Origin': '*',
       },
     });

src/components/map/DualMapView.tsx

@@ -13,7 +13,7 @@ const MapView = dynamic(() => import('./MapView'), {
   loading: () => <MapLoading />,
 });
 
-const IndoorMapView = dynamic(() => import('./IndoorMapView'), {
+const C3NavEmbed = dynamic(() => import('./C3NavEmbed'), {
   ssr: false,
   loading: () => <MapLoading />,
 });
@@ -139,13 +139,11 @@ export default function DualMapView({
           onClearRoute={clearRoute}
         />
       ) : (
-        <IndoorMapView
+        <C3NavEmbed
           eventId={eventId}
           participants={participants}
           currentUserId={currentUserId}
-          onParticipantClick={handleParticipantClick}
-          onSwitchToOutdoor={goOutdoor}
-          onPositionSet={onIndoorPositionSet}
+          onToggleOutdoor={goOutdoor}
         />
       )}