fix: Use only dist folder (contains public assets)

- Astro build automatically copies public/ to dist/
- Remove separate public folder copy (not needed)
- Use PORT environment variable (default 80)
- Fix favicon 404 by using correct dist structure

.docker/Dockerfile

@@ -0,0 +1,14 @@
+# Astro Production Dockerfile
+FROM node:20-alpine
+
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci --omit=dev
+
+COPY . .
+RUN npm run build
+
+EXPOSE 4321
+
+CMD ["npm", "run", "preview", "--", "--host", "0.0.0.0", "--port", "4321"]