Stop tracking app.ini to prevent runtime secrets from blocking git pull

Gitea populates secret fields (LFS_JWT_SECRET, SECRET_KEY, etc.) at
startup, causing app.ini to always show as modified. Since secrets are
already passed via environment variables, the tracked file is replaced
with an ignored app.ini and a tracked app.ini.template for reference.

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

.gitignore

@@ -5,6 +5,7 @@ certbot/www
 backend/token/
 .env
 
+gitea/config/app.ini
 gitea/data/*
 gitea-runner/data/*