feat(chat): show first recharge offer in header

src/app/chat/components/chat-header.tsx

@@ -5,6 +5,7 @@
  * 图标：lucide-react <Lock />（游客 banner）+ <Menu />（菜单按钮）
  *   tree-shakable，currentColor 继承父 color
  */
+import type { ReactNode } from "react";
 import { Lock, Menu } from "lucide-react";
 import { useRouter } from "next/navigation";
 
@@ -14,9 +15,10 @@ import styles from "./chat-header.module.css";
 
 export interface ChatHeaderProps {
   isGuest: boolean;
+  offerBanner?: ReactNode;
 }
 
-export function ChatHeader({ isGuest }: ChatHeaderProps) {
+export function ChatHeader({ isGuest, offerBanner }: ChatHeaderProps) {
   const router = useRouter();
 
   if (isGuest) {
@@ -37,6 +39,8 @@ export function ChatHeader({ isGuest }: ChatHeaderProps) {
 
   return (
     <header className={styles.header}>
+      {offerBanner}
+
       <div className={styles.headerRow}>
         {/* 菜单按钮（点击 → push 到 /sidebar，与 Dart MenuButton 一致） */}
         <button