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>

docker/nginx.conf

@@ -0,0 +1,29 @@
+server {
+  listen 8080;
+  server_name _;
+
+  root /usr/share/nginx/html;
+  index index.html;
+
+  add_header X-Content-Type-Options nosniff always;
+  add_header X-Frame-Options DENY always;
+  add_header Referrer-Policy strict-origin-when-cross-origin always;
+
+  # Static assets: cache aggressively
+  location ~* \.(?:css|js|mjs|map|png|jpg|jpeg|gif|svg|ico|webp|woff2|woff|ttf)$ {
+    expires 30d;
+    add_header Cache-Control "public, max-age=2592000, immutable";
+    try_files $uri =404;
+  }
+
+  # HTML: no cache
+  location ~* \.html$ {
+    add_header Cache-Control "no-cache";
+    try_files $uri =404;
+  }
+
+  # Next.js static export: try file, then file.html, then 404
+  location / {
+    try_files $uri $uri.html $uri/ /404.html;
+  }
+}