chore: 去掉未上线前的旧兼容垫片，板块流收口到首页

鉴权只认 cookie、SEO 只走 Next、sort 与推荐对齐；删除 Bearer、Go sitemap、post_type 回填等冗余路径。

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

backend/service/post.go

@@ -29,7 +29,7 @@ type PostListQuery struct {
 	BoardID     uint
 	Page        int
 	Size        int
-	Sort        string // latest | hot | new
+	Sort        string // latest | recommended | new
 	Keyword     string // 搜索关键词
 	Recommended bool   // 仅精华帖
 	ViewerID    uint   // 当前查看者（0=游客）
@@ -209,7 +209,7 @@ func (s *PostService) List(q PostListQuery) ([]PostListItem, int64, error) {
 		SELECT MAX(c.created_at) FROM comments c
 		WHERE c.post_id = posts.id AND c.status = 'published' AND c.deleted_at IS NULL
 	), created_at)) DESC`
-	if q.Sort == "hot" {
+	if q.Sort == "recommended" {
 		order = "pinned DESC, (like_count + comment_count * 2) DESC, created_at DESC"
 	}
 	// new：纯按发帖时间（新帖子）