User-Löschen: Upgrade-Anfragen + Hund-Daten mit aufräumen (Admin + Self-Delete)

- admin.py delete_user: löscht jetzt auch Hund-zentrierte Daten (diary,
  health, training_sessions, training_streaks, expenses), dogs,
  upgrade_requests, push_subscriptions, notifications, forum_posts
  bevor der User-Row weg ist. Vorher: nur DELETE FROM users → Waisen in
  allen FK-Tabellen.
- profile.py delete_account: gleicher Cleanup-Set, vergisst jetzt
  upgrade_requests nicht mehr.
- admin.py Dashboard-Counter 'Zu Erledigen': JOIN users, damit
  verwaiste Anfragen nicht mehr im Header-Badge erscheinen (Liste
  selbst filtert sie schon korrekt via JOIN). Bump 1135→1136.

backend/routes/profile.py

@@ -164,6 +164,7 @@ async def delete_account(user=Depends(get_current_user)):
             conn.execute("DELETE FROM training_streaks WHERE dog_id=?", (did,))
             conn.execute("DELETE FROM expenses WHERE dog_id=?", (did,))
         conn.execute("DELETE FROM dogs WHERE user_id=?", (uid,))
+        conn.execute("DELETE FROM upgrade_requests WHERE user_id=?", (uid,))
         conn.execute("DELETE FROM push_subscriptions WHERE user_id=?", (uid,))
         conn.execute("DELETE FROM notifications WHERE user_id=?", (uid,))
         conn.execute("DELETE FROM forum_posts WHERE user_id=?", (uid,))