feat: 实现全局响应式布局，适配不同设备、不同屏幕、不同分辨率

- 统一断点体系：560px(手机)、900px(平板)、1180px(小桌面)
- Shell导航：900px底部导航条、560px紧凑布局、顶栏触控优化
- 电商页面：三栏布局在平板/手机下改为单栏堆叠+横向标签切换
- 工作台：启动页编辑器全宽、消息气泡适配窄屏、建议标签换行
- 画布页面：工具栏横向滚动、节点缩小、手机全屏操作
- 社区/资产库/工具页/数字人等全部17个页面补齐响应式断点
- 新增32条@media规则，媒体查询从107条增至139条

src/styles/pages/community.css

@@ -117,3 +117,52 @@
   font-weight: 600;
   line-height: 1.6;
 }
+
+/* ═══════════════════════════════════════════════════════
+   Responsive: Community
+   Breakpoints: 900px / 560px
+   ═══════════════════════════════════════════════════════ */
+
+@media (max-width: 900px) {
+  .community-page {
+    padding: 12px 16px 80px;
+  }
+
+  .community-carousel__slide--video {
+    min-height: 200px;
+  }
+
+  .community-carousel__video {
+    max-height: 220px;
+  }
+
+  .community-case-card__preview {
+    min-height: 140px;
+  }
+}
+
+@media (max-width: 560px) {
+  .community-page {
+    padding: 10px 10px 80px;
+  }
+
+  .community-carousel__slide--video {
+    min-height: 160px;
+  }
+
+  .community-carousel__video {
+    max-height: 180px;
+  }
+
+  .community-case-card__preview {
+    min-height: 110px;
+  }
+
+  .community-case-empty {
+    padding: 32px 16px;
+  }
+
+  .community-case-empty__icon {
+    font-size: 18px;
+  }
+}