feat: 公开页背景色支持 iframe 外部配置 + CM助手旁排行榜入口

- 新增 usePublicBackground:公开页(排行榜/分享/会商分享/计划任务)支持
  嵌套方通过 ?bg=/?text= 查询参数或 postMessage 覆盖背景/文字色
- Header 左上角 CM助手 旁新增「排行榜」按钮,新标签打开公开排行榜页

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/pages/PublicScheduledTaskPage.tsx

@@ -43,6 +43,7 @@ import {
 import { MarkdownContent } from "@/components/workspace/messages/markdown-content";
 import { HtmlPreviewFrame } from "@/components/html-preview-frame";
 import { getBackendBaseURL } from "@/core/config";
+import { usePublicBackground } from "@/core/embed/background";
 import { downloadMarkdownAsDocx } from "@/core/scheduled-tasks/markdown-docx";
 import { reasoningPlugins } from "@/core/streamdown";
 import { cn } from "@/lib/utils";
@@ -289,6 +290,8 @@ export default function PublicScheduledTaskPage() {
   const [runListWidth, setRunListWidth] = useState(RUN_LIST_DEFAULT_WIDTH);
   const dragStateRef = useRef<{ startX: number; startWidth: number } | null>(null);
   const queryClient = useQueryClient();
+  // 嵌套方可用 ?bg=/?text= 或 postMessage 覆盖背景/文字色。
+  const pageBg = usePublicBackground();
 
   const { data, isLoading, isError, error } = useQuery({
     queryKey: ["public-scheduled-task", taskId],
@@ -405,7 +408,7 @@ export default function PublicScheduledTaskPage() {
 
   if (!taskId) {
     return (
-      <div className="text-muted-foreground flex h-screen items-center justify-center text-sm">
+      <div className="text-muted-foreground flex h-screen items-center justify-center text-sm" style={pageBg}>
         缺少任务 ID。请使用 <code className="mx-1">/public/scheduled-tasks/&lt;task_id&gt;</code>。
       </div>
     );
@@ -413,7 +416,7 @@ export default function PublicScheduledTaskPage() {
 
   if (isLoading) {
     return (
-      <div className="text-muted-foreground flex h-screen items-center justify-center gap-2 text-sm">
+      <div className="text-muted-foreground flex h-screen items-center justify-center gap-2 text-sm" style={pageBg}>
         <Loader2 className="size-4 animate-spin" />
         正在加载任务记录...
       </div>
@@ -422,7 +425,7 @@ export default function PublicScheduledTaskPage() {
 
   if (isError) {
     return (
-      <div className="text-destructive flex h-screen items-center justify-center text-sm">
+      <div className="text-destructive flex h-screen items-center justify-center text-sm" style={pageBg}>
         加载失败：{error instanceof Error ? error.message : "未知错误"}
       </div>
     );
@@ -430,7 +433,7 @@ export default function PublicScheduledTaskPage() {
 
   return (
     <TooltipProvider delayDuration={150}>
-      <div className="bg-muted/20 flex h-screen min-h-0 overflow-hidden p-4">
+      <div className="bg-muted/20 flex h-screen min-h-0 overflow-hidden p-4" style={pageBg}>
         <div
           className="relative flex min-h-0 shrink-0 transition-[width] duration-200 ease-out"
           style={{ width: visibleRunListWidth }}
@@ -1139,6 +1142,8 @@ function RunDetailPane({ run, taskId }: { run: PublicRun; taskId: string }) {
 
 export function PublicScheduledTaskFullscreenPage() {
   const { taskId, runId } = useParams<{ taskId: string; runId: string }>();
+  // 嵌套方可用 ?bg=/?text= 或 postMessage 覆盖背景/文字色。
+  const pageBg = usePublicBackground();
   const [searchParams] = useSearchParams();
   const requestedTab = searchParams.get("tab");
   const tabKind: ContentTab["kind"] =
@@ -1194,7 +1199,7 @@ export function PublicScheduledTaskFullscreenPage() {
 
   return (
     <TooltipProvider delayDuration={150}>
-      <div className="bg-background flex h-screen min-h-0 flex-col">
+      <div className="bg-background flex h-screen min-h-0 flex-col" style={pageBg}>
         <div className="flex h-12 shrink-0 items-center gap-2 border-b px-3">
           <Button asChild variant="ghost" size="sm" className="h-8 px-2 text-xs">
             <a href={backHref}>