chore: add Dockerfile and docker-compose with static file serving

Multi-stage Docker build (web → server → production). Fastify serves
React build in production with SPA fallback. Docker Compose with volume
for SQLite persistence.

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

docker-compose.yml

@@ -0,0 +1,21 @@
+version: "3.8"
+
+services:
+  spelljammer:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: spelljammer-ships
+    ports:
+      - "3000:3000"
+    volumes:
+      - spelljammer-data:/data
+    environment:
+      - NODE_ENV=production
+      - PORT=3000
+      - DB_PATH=/data/spelljammer.sqlite
+    restart: unless-stopped
+
+volumes:
+  spelljammer-data:
+    driver: local