Add Dockerfile for self-hosted deployment

Multi-stage: Hugo builder + nginx:alpine to serve static output.

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

Dockerfile

@@ -0,0 +1,9 @@
+FROM hugomods/hugo:exts as builder
+
+WORKDIR /site
+COPY . .
+RUN git submodule update --init --recursive && hugo --minify
+
+FROM nginx:alpine
+COPY --from=builder /site/public /usr/share/nginx/html
+EXPOSE 80