feat: Web Push für Logbuch-Eigner bei Crew-Sync

Benachrichtigt Owner optional per VAPID/Web Push, wenn Collaborators
Änderungen synchronisieren — ohne Klartext-Inhalte, mit Opt-in in den
Einstellungen, Custom Service Worker und Deep-Link zum Logbuch.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/services/analytics.ts

@@ -20,7 +20,9 @@ export const PlausibleEvents = {
   PHOTO_UPLOADED: 'Photo Uploaded',
   BACKUP_EXPORTED: 'Backup Exported',
   BACKUP_RESTORED: 'Backup Restored',
-  DEMO_OPENED: 'Demo Opened'
+  DEMO_OPENED: 'Demo Opened',
+  PUSH_ENABLED: 'Push Enabled',
+  PUSH_DISABLED: 'Push Disabled'
 } as const
 
 export type PlausibleEventName = (typeof PlausibleEvents)[keyof typeof PlausibleEvents]