Add CI/CD: Dockerfile + Gitea Actions workflow

- Multi-stage Dockerfile with Bun 1.3.6
- Gitea Actions workflow for auto-build
- Push to git.fuq.tv container registry
- Build cache optimization

Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,11 @@
+node_modules
+.git
+.gitignore
+.env
+.env.*
+!.env.example
+*.log
+dist
+.DS_Store
+README.md
+.cursor