Match the GitHub App endpoint picker so self-hosted / tunnel setups can
select FQDN, IP, app URL, or a custom base. Redirect URI is derived as
{base}/webhooks/source/gitlab/redirect and persisted for token exchange.
The secret was always stored encrypted, but the setup form wiped the
input on every load. Load it back for admins (GitHub App parity) so a
reload no longer looks like a failed save.
Use the red incomplete-setup alert like GitHub, keep name + OAuth
credentials front-and-center, and tuck GitLab URL / API / SSH / system
wide options into an Advanced accordion for self-hosted users.
Andras Bacsai