feat(chat): add private message unlock flow

src/app/chat/components/message-content.tsx

@@ -10,19 +10,35 @@
  *   - 两者都有：图片在上，文字在下
  */
 import { ImageBubble } from "./image-bubble";
+import { PrivateMessageCard } from "./private-message-card";
 import { TextBubble } from "./text-bubble";
 
 export interface MessageContentProps {
+  messageId?: string;
   content: string;
   imageUrl?: string | null;
   isFromAI: boolean;
+  privateLocked?: boolean | null;
+  privateHint?: string | null;
+  isUnlockingPrivate?: boolean;
+  onUnlockPrivateMessage?: (messageId: string) => void;
 }
 
 const IMAGE_PLACEHOLDER = "[图片]";
 
-export function MessageContent({ content, imageUrl, isFromAI }: MessageContentProps) {
+export function MessageContent({
+  messageId,
+  content,
+  imageUrl,
+  isFromAI,
+  privateLocked,
+  privateHint,
+  isUnlockingPrivate = false,
+  onUnlockPrivateMessage,
+}: MessageContentProps) {
   const hasImage = imageUrl != null && imageUrl.length > 0;
   const hasText = content.length > 0 && content !== IMAGE_PLACEHOLDER;
+  const isLockedPrivateMessage = privateLocked === true;
 
   return (
     <div
@@ -37,8 +53,22 @@ export function MessageContent({ content, imageUrl, isFromAI }: MessageContentPr
         gap: 8,
       }}
     >
-      {hasImage && imageUrl && <ImageBubble imageUrl={imageUrl} />}
-      {hasText && <TextBubble content={content} isFromAI={isFromAI} />}
+      {isLockedPrivateMessage ? (
+        <PrivateMessageCard
+          hint={privateHint}
+          isUnlocking={isUnlockingPrivate}
+          onUnlock={
+            messageId
+              ? () => onUnlockPrivateMessage?.(messageId)
+              : undefined
+          }
+        />
+      ) : (
+        <>
+          {hasImage && imageUrl && <ImageBubble imageUrl={imageUrl} />}
+          {hasText && <TextBubble content={content} isFromAI={isFromAI} />}
+        </>
+      )}
     </div>
   );
 }