Gitignore gitea app.ini and remove INTERNAL_TOKEN from template

Runtime config (app.ini) should not be tracked since secrets are
injected via env vars in docker-compose. The template remains as
source of truth. INTERNAL_TOKEN is removed from the template as
it is set exclusively via GITEA__security__INTERNAL_TOKEN env var.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

gitea/config/app.ini.template

@@ -60,7 +60,6 @@ INSTALL_LOCK = true
 SECRET_KEY = 
 REVERSE_PROXY_LIMIT = 1
 REVERSE_PROXY_TRUSTED_PROXIES = *
-INTERNAL_TOKEN =
 PASSWORD_HASH_ALGO = pbkdf2
 
 [service]