feat: add Gitea self-hosted Git service with Actions runner

- Create new 'dev' stack at dev.pivoine.art
- Add Gitea with PostgreSQL database (core stack)
- Add Gitea Actions runner with Docker support
- Enable mailer configuration via SMTP
- Enable container registry and packages
- Add gitea database to PostgreSQL init script

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

compose.yaml

@@ -21,6 +21,7 @@ include:
   - proxy/compose.yaml
   - watch/compose.yaml
   - media/compose.yaml
+  - dev/compose.yaml
 
 networks:
   compose_network: