Delete / disable user account (backend) #89

Allow users to permanently delete or temporarily disable their account.

Backend

• POST /api/users/me/delete – permanently deletes account and all associated data (messages, tokens, files)
• POST /api/users/me/disable – disables the account (user can re‑activate later)
• Handle cleanup: remove from groups, notify contacts (optional), schedule data removal

Make sure the process is irreversible for deletion and that data protection is respected.