ci(github actions): 配置buildx并添加缓存清理步骤

配置Docker Buildx的构建器名称并启用持久化，在任务结束时始终清理Buildx缓存

.github/workflows/ci.yml

@@ -246,6 +246,9 @@ jobs:
 
       - name: 设置 Docker Buildx
         uses: docker/setup-buildx-action@v3
+        with:
+          name: myaps-builder
+          use: true
 
       - name: 登录镜像仓库
         uses: docker/login-action@v3
@@ -450,3 +453,10 @@ jobs:
           echo "2. 按租户需求修改环境变量"
           echo "3. 使用统一镜像部署，注入租户配置"
           echo "=========================================="
+
+      - name: 清理 Buildx 缓存
+        if: always()
+        run: |
+          echo "清理 Buildx 构建缓存..."
+          docker buildx prune -f
+          echo "✅ 清理完成"