chore: 优化后端构建方式

apps/backend/Dockerfile

@@ -8,14 +8,16 @@ RUN pnpm install --frozen-lockfile
 COPY . .
 RUN pnpm run build
 
-FROM node:22-alpine
-RUN npm install -g pnpm
+RUN CI=true pnpm prune --prod
+
+FROM node:22-alpine AS runner
 WORKDIR /app
 
-COPY package.json pnpm-lock.yaml ./
-RUN pnpm install --frozen-lockfile --prod
+ENV NODE_ENV=production
 
+COPY --from=builder /app/node_modules ./node_modules
 COPY --from=builder /app/dist ./dist
+COPY --from=builder /app/package.json ./package.json
 
 EXPOSE 3001
 CMD ["node", "dist/main.js"]