add Docker and CI/CD pipeline with ledo

Configure Next.js static export with nginx serving, Dockerfile
(multi-stage build), docker-compose for prod/dev, Gitea Actions
pipelines for build-on-push and tag-based releases using ledo tool.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

next.config.ts

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