feat(infra): add production Dockerfile and docker-compose.prod.yml

Multi-stage alpine-based build, healthcheck on /api/health, /data volume.
Verified end-to-end: image builds, container starts, health returns 200.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,39 @@
+# syntax=docker/dockerfile:1.7
+
+FROM node:22-alpine AS builder
+WORKDIR /app
+
+# Alpine needs build tools for better-sqlite3 native module
+RUN apk add --no-cache python3 make g++ libc6-compat
+
+COPY package*.json ./
+RUN npm ci
+
+COPY . .
+RUN npm run build
+
+# Remove dev dependencies for the runtime image
+RUN npm prune --omit=dev
+
+FROM node:22-alpine AS runner
+WORKDIR /app
+
+RUN apk add --no-cache libc6-compat
+
+COPY --from=builder /app/build ./build
+COPY --from=builder /app/node_modules ./node_modules
+COPY --from=builder /app/package.json ./package.json
+
+ENV NODE_ENV=production
+ENV HOST=0.0.0.0
+ENV PORT=3000
+ENV DATABASE_PATH=/data/kochwas.db
+ENV IMAGE_DIR=/data/images
+
+VOLUME ["/data"]
+EXPOSE 3000
+
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
+  CMD wget -qO- http://localhost:3000/api/health > /dev/null || exit 1
+
+CMD ["node", "build/index.js"]