Add web push notification system for user engagement and updates

Implement a web push notification system, including service worker integration, user subscription management, and an admin interface for sending broadcast messages.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 23852c00-4779-460a-9e0c-d09fee4b6c92
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: f585829f-898b-492f-82a5-11f4a76c87fb
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/f209e72a-0939-48fa-84fc-57854de71967/23852c00-4779-460a-9e0c-d09fee4b6c92/ICRgny1
Replit-Helium-Checkpoint-Created: true

replit.md

@@ -17,6 +17,7 @@ The official website for Folx Music Television (folx.tv). Dark-themed bento grid
 - Recipe widget + full /rezepte subpage (21 recipes across 5 regions: Österreich, Bayern, Schwaben/Baden, Südtirol/Alpen, Norddeutschland) with AI-generated images
 - Google News RSS widget (Volksmusik/Schlager news, 5 items, auto-rotate)
 - Google AdSense integration (ca-pub-4465464714854276)
+- Web Push Notifications (bell icon in header, admin panel at /admin/push)
 - Article listing with featured carousel and category filtering
 - HTML content supports embedded iframes (bunny.net, YouTube, Facebook, Instagram, TikTok)
 - DOMPurify sanitization for safe HTML rendering
@@ -46,6 +47,11 @@ The official website for Folx Music Television (folx.tv). Dark-themed bento grid
 - `PATCH /api/articles/:id` - Update article
 - `DELETE /api/articles/:id` - Delete article
 - `POST /api/upload` - Upload image file
+- `GET /api/push/vapid-key` - Get VAPID public key for push subscriptions
+- `POST /api/push/subscribe` - Subscribe to push notifications
+- `POST /api/push/unsubscribe` - Unsubscribe from push notifications
+- `GET /api/push/count` - Get push subscriber count
+- `POST /api/admin/push/send` - Send push notification to all subscribers
 - `GET /api/gallery` - Shuffled gallery images from Cloudinary (with artist names from filenames + overrides)
 - `GET /api/gallery/focal-points` - Gallery image focal points (JSON)
 - `PUT /api/gallery/focal-points/:fileName` - Set focal point for gallery image