feat(desec): add deSEC account + domain registration backend

Add the server-side deSEC (dedyn.io) free dynamic-DNS flow so users without a
domain can obtain one from the AIO interface.

- DesecManager drives the full flow against the deSEC API, matching its real
  semantics: account creation returns HTTP 202 + email verification (no token),
  a token is obtained via /auth/login/ only after the email is verified, domain
  registration handles 201/409, and a wildcard CNAME rrset is created for new
  accounts. Existing accounts can be used by supplying a password.
- The "awaiting verification" step is derived from the stored credentials (email
  + generated password but no token and no domain yet), not a separate flag.
  register() returns false for that state so the controller can re-render the
  awaiting-verification UI instead of surfacing it as an error.
- DesecController exposes POST /api/desec/register; DependencyInjection wires the
  manager; account credentials (email, generated password, token) are stored in
  the AIO configuration and DESEC_TOKEN is exposed to the caddy container.
- The dynamic-DNS record is refreshed with the current public IP on container
  start (DockerController) and via the cron path (Cron/UpdateDesecIp, cron.sh).
- Fix an undefined-variable bug in the desecToken/desecPassword config setters
  that prevented credentials from being persisted.

Co-Authored-By: szaimen <42591237+szaimen@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Simon L. <szaimen@e.mail.de>

Containers/mastercontainer/cron.sh

@@ -57,6 +57,9 @@ while true; do
     # Check if AIO is outdated
     sudo -E -u www-data php /var/www/docker-aio/php/src/Cron/OutdatedNotification.php
 
+    # Update deSEC DNS IP record (no-op when IP is unchanged or deSEC is not configured)
+    sudo -E -u www-data php /var/www/docker-aio/php/src/Cron/UpdateDesecIp.php
+
     # Remove sessions older than 24h
     find "/mnt/docker-aio-config/session/" -mindepth 1 -mmin +1440 -delete