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/components/PostComposer.tsx

@@ -1220,7 +1220,11 @@ export default function PostComposer(props: PostComposerProps) {
                       <div className="truncate text-[13.5px]">{a.name}</div>
                       <div className="meta text-[12px]">{formatSize(a.size)}</div>
                     </div>
-                    <label className="meta text-[12px] flex items-center gap-1.5 shrink-0">
+                    <label
+                      className={`meta text-[12px] flex items-center gap-1.5 shrink-0${
+                        a.price_points > 0 ? " j13-compose-att-paid" : ""
+                      }`}
+                    >
                       积分
                       <input
                         type="number"
@@ -1231,6 +1235,7 @@ export default function PostComposer(props: PostComposerProps) {
                         onChange={(e) => void setAttPrice(a.id, Number(e.target.value))}
                         className="j13-compose-field !py-1 !px-2 w-20 text-[13px]"
                         data-tip="0 = 免费下载"
+                        aria-label={`${a.name} 下载积分，0 为免费`}
                       />
                     </label>
                     <button