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>

next.config.ts

@@ -1,7 +1,7 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
 };
 
 export default nextConfig;