Add Docker deployment pipeline and site updates

- Dockerfile (multi-stage Next.js standalone build)
- docker-compose.yml for Portainer stack
- Gitea Actions workflow for CI/CD
- Runner container config (Dockerfile.runner + compose)
- next.config.ts: enable standalone output
- Site content and image updates

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

Dockerfile.runner

@@ -0,0 +1,2 @@
+FROM gitea/act_runner:latest
+RUN apk add --no-cache docker-cli docker-cli-compose git bash nodejs