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

src/app/chat/components/chat-header.module.css

@@ -0,0 +1,56 @@
+/* ChatHeader 顶部栏样式 */
+
+.header {
+  flex: 0 0 auto;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: var(--spacing-4, 16px) var(--spacing-5, 20px);
+  background: var(--color-header-background, rgba(0, 0, 0, 0.3));
+}
+
+.guestBanner {
+  width: 100%;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: var(--spacing-2, 8px);
+  padding: var(--spacing-2, 8px) var(--spacing-4, 16px);
+  background: var(--color-accent, #f84d96);
+  color: #fff;
+  font-size: var(--font-size-sm, 12px);
+  font-weight: 500;
+  cursor: pointer;
+  border: 0;
+  text-align: center;
+}
+
+.guestBannerIcon {
+  width: var(--icon-size-sm, 16px);
+  height: var(--icon-size-sm, 16px);
+}
+
+.headerRow {
+  width: 100%;
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  padding: 0 var(--spacing-4, 16px);
+}
+
+.menuButton {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: var(--spacing-2, 8px);
+  background: var(--color-dark-background, #111)cc;
+  border-radius: 9999px;
+  border: 0;
+  cursor: pointer;
+  color: var(--color-text-primary, #fff);
+}
+
+.menuIcon {
+  width: var(--icon-size-xl, 32px);
+  height: var(--icon-size-xl, 32px);
+}