feat(chat): port chat widget components from Dart to React

src/app/chat/components/chat-menu-bar.module.css

@@ -0,0 +1,69 @@
+/* ChatMenuBar 菜单栏样式 */
+
+.overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 60;
+}
+
+.backdrop {
+  position: absolute;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.4);
+}
+
+.menu {
+  position: absolute;
+  top: 56px;
+  right: 12px;
+  min-width: 200px;
+  background: var(--color-surface, #1f1a2e);
+  border: 1px solid rgba(255, 255, 255, 0.1);
+  border-radius: var(--radius-md, 8px);
+  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.4);
+  padding: var(--spacing-1, 4px) 0;
+  display: flex;
+  flex-direction: column;
+  overflow: hidden;
+}
+
+.item {
+  display: flex;
+  align-items: center;
+  gap: var(--spacing-3, 12px);
+  padding: var(--spacing-3, 12px) var(--spacing-4, 16px);
+  background: transparent;
+  border: 0;
+  border-radius: 0;
+  color: var(--color-text-primary, #fff);
+  font-size: var(--font-size-base, 14px);
+  text-align: left;
+  cursor: pointer;
+  width: 100%;
+}
+
+.item:hover,
+.item:focus-visible {
+  background: rgba(255, 255, 255, 0.08);
+}
+
+.itemIcon {
+  font-size: 18px;
+  width: 20px;
+  text-align: center;
+}
+
+.divider {
+  height: 1px;
+  background: rgba(255, 255, 255, 0.1);
+  margin: var(--spacing-1, 4px) 0;
+}
+
+.badge {
+  margin-left: auto;
+  font-size: var(--font-size-xs, 11px);
+  padding: 2px 6px;
+  background: var(--color-accent, #f84d96);
+  color: #fff;
+  border-radius: 9999px;
+}