Adds deploy/gitea/app.ini with hardened [service] settings and
scripts/harden_gitea.sh to apply them on the server. The script
backs up the existing config, patches the four required settings,
restarts Gitea, and verifies the changes.
Settings applied:
- DISABLE_REGISTRATION = true
- ALLOW_ONLY_EXTERNAL_REGISTRATION = false
- SHOW_REGISTRATION_BUTTON = false
- REQUIRE_SIGNIN_VIEW = true
Fixes#988
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>