feat(attach): 付费附件游客跳登录，积分数独立价签并升级下载交互

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

frontend/app/post/[id]/page.tsx

@@ -727,7 +727,11 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
                 components={{ h2: headingRenderer("h2"), h3: headingRenderer("h3") }}
               />
 
-              <PostAttachments postId={post.id} items={post.attachments || []} />
+              <PostAttachments
+                postId={post.id}
+                items={post.attachments || []}
+                loggedIn={!!me.user}
+              />
 
               {/* 类型特殊块（投票/悬赏/抽奖/问答）统一放正文最下方 */}
               <PostInteractPanels