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/shell/app-shell.css

@@ -540,3 +540,101 @@
   overflow: auto;
   scrollbar-color: rgba(var(--accent-rgb), 0.42) transparent;
 }
+
+/* ═══════════════════════════════════════════════════════
+   Responsive: Shell Navigation & Topbar
+   Breakpoints: 1180px (small desktop), 900px (tablet),
+   560px (phone). Complements legacy-components.css rules.
+   ═══════════════════════════════════════════════════════ */
+
+/* ── 1180px: Compact topbar ── */
+@media (max-width: 1180px) {
+  .brand-lockup__tone {
+    display: none;
+  }
+  .creator-button {
+    display: none;
+  }
+  .member-button {
+    max-width: 148px;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+  }
+}
+
+/* ── 900px: Bottom nav & Touch-friendly topbar ── */
+@media (max-width: 900px) {
+  .web-topbar {
+    position: sticky;
+    top: 0;
+    flex: 0 0 52px;
+    padding: 8px 12px;
+    gap: 10px;
+  }
+
+  .brand-lockup__name {
+    max-width: 110px;
+    overflow: hidden;
+    text-overflow: ellipsis;
+  }
+
+  .creator-button,
+  .member-button {
+    display: none;
+  }
+
+  .profile-button span:last-child {
+    display: none;
+  }
+
+  .profile-button {
+    min-width: 44px;
+    height: 44px;
+    padding: 0;
+    aspect-ratio: 1;
+  }
+
+  .icon-button {
+    min-width: 44px;
+    height: 44px;
+  }
+
+  .web-shell__page {
+    padding-bottom: 78px;
+  }
+
+  .floating-page-scroll-actions {
+    display: none;
+  }
+}
+
+/* ── 560px: Phone-sized compact layout ── */
+@media (max-width: 560px) {
+  .web-topbar {
+    flex: 0 0 44px;
+    padding: 6px 10px;
+    gap: 6px;
+  }
+
+  .brand-lockup {
+    gap: 6px;
+  }
+
+  .brand-lockup__mark {
+    width: 24px;
+    height: 24px;
+    border-radius: 6px;
+  }
+
+  .brand-lockup__name {
+    font-size: 13px;
+    max-width: 80px;
+  }
+
+  .profile-button,
+  .icon-button {
+    min-width: 36px;
+    height: 36px;
+  }
+}