Fills the gaps between the admin panel screens and the backend: a full
free-text + slide-count + language -> AI-generated presentation flow with
new slide-cloning logic in TemplateFillService, a "my presentations" list
endpoint, a swappable payment-gateway structure for wallet top-ups (fake
driver for now), and avatar upload / public-profile toggle / account
deletion / password change / notification preference endpoints.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
