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>

Dockerfile

@@ -0,0 +1,43 @@
+# ---- Stage 1: Build the React frontend ----
+FROM node:18-alpine AS web-build
+WORKDIR /app/web
+COPY web/package.json web/package-lock.json ./
+RUN npm ci
+COPY web/ ./
+RUN npm run build
+
+# ---- Stage 2: Build the Node.js server ----
+FROM node:18-alpine AS server-build
+WORKDIR /app/server
+COPY server/package.json server/package-lock.json ./
+RUN npm ci
+COPY server/ ./
+RUN npm run build
+
+# ---- Stage 3: Production image ----
+FROM node:18-alpine AS production
+WORKDIR /app
+
+# Copy server package files and install production deps only
+COPY server/package.json server/package-lock.json ./
+RUN npm ci --omit=dev
+
+# Copy compiled server
+COPY --from=server-build /app/server/dist ./dist
+
+# Copy server migration files (needed at runtime)
+COPY --from=server-build /app/server/src/db/migrations ./dist/db/migrations
+
+# Copy frontend build output
+COPY --from=web-build /app/web/dist ./web-dist
+
+# Create data directory for SQLite
+RUN mkdir -p /data
+
+ENV NODE_ENV=production
+ENV PORT=3000
+ENV DB_PATH=/data/spelljammer.sqlite
+
+EXPOSE 3000
+
+CMD ["node", "dist/index.js"]