feat: add notifications system with bell badge, polling, Directus flows, and webhook integration

AGENTS.md

@@ -64,7 +64,8 @@ js/
 │   ├── currency.js     # XMR/Fiat Umrechnung
 │   ├── pow-captcha.js  # Proof-of-Work Captcha (Challenge/Verify)
 │   ├── btcpay.js       # BTCPay Server Integration (Invoice, Checkout, Webhook)
-│   └── favorites.js    # Favoriten-Service (localStorage + Directus Sync)
+│   ├── favorites.js    # Favoriten-Service (localStorage + Directus Sync)
+│   └── notifications.js # Benachrichtigungen (Polling, Badge)
 └── components/
     ├── app-shell.js    # Layout, registriert Routes
     ├── app-header.js   # Header (Theme-Toggle, Lang-Dropdown, Profil-Dropdown)
@@ -147,7 +148,8 @@ locales/
 8. ~~Favoriten Directus Sync~~ ✅ FavoritesService mit Union-Merge bei Login
 9. ~~Expired Listings~~ ✅ Directus Flow (alle 15 Min), Status-Badges auf Cards
 10. Reputation-System (5/15/50 Deals Stufen)
-11. Push-Benachrichtigungen für neue Nachrichten
+11. ~~In-App Benachrichtigungen~~ ✅ NotificationsService mit Polling, Glocke-Icon mit Badge
+12. Push-Benachrichtigungen (Web Push API)
 
 ## Directus Berechtigungen (Public-Rolle)
 
@@ -163,12 +165,15 @@ locales/
 | `conversations` | ✓ | ✓ | ✓ | Filter via `participant_hash`, Update nur `status` |
 | `messages` | ✓ | ✓ | - | Filter via `conversation` ID |
 | `favorites` | ✓ | ✓ | - | User-Rolle: Filter `user = $CURRENT_USER`, Delete erlaubt |
+| `notifications` | ✓ | ✓ (via Flow/Webhook) | ✓ | User-Rolle: Filter `user_hash`, nur `read` updaten |
 
 ### Directus Flows
 
 | Flow | Trigger | Aktion |
 |------|---------|--------|
 | Archive Expired Listings | Schedule `*/15 * * * *` | `status → archived` wenn `expires_at < NOW` |
+| Notify: Listing Published | Webhook (btcpay-webhook.php) | Creates notification when listing is published after payment |
+| Notify: New Message | Event Hook `items.create` on `messages` | Creates notification for message recipient |
 
 Siehe `docs/DIRECTUS-SCHEMA.md` für vollständiges Schema.