Add docker-compose.yml for single-command deployment

Runs the portfolio with: docker compose up --build

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

docker-compose.yml

@@ -0,0 +1,12 @@
+services:
+  portfolio:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: portfolio:latest
+    container_name: portfolio
+    ports:
+      - "3000:3000"
+    restart: unless-stopped
+    environment:
+      - NODE_ENV=production