feat(ui): 浅蓝主题、外观设置与圆桌看板主题适配，优化工作区布局

新增 lightblue 主题与外观设置联动，圆桌 Step3 看板/report 统一配色；工作区侧边栏、输入框与轻应用 iframe 主题参数同步更新。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend-web/src/core/system-settings/api.ts

@@ -135,7 +135,7 @@ export async function updatePublishSquares(
   return (await response.json()) as PublishSquaresSettings;
 }
 
-export type ThemeMode = "light" | "dark";
+export type ThemeMode = "light" | "dark" | "lightblue";
 export type ViewMode = "card" | "list";
 
 export interface AppearanceSettings {