feat: 帖子分级置顶（板块/全站）与板块管理员置顶权限、消息管理权限调整

backend/service/legacyimport.go

@@ -226,6 +226,14 @@ type legacyPostRow struct {
 
 func (legacyPostRow) TableName() string { return "posts" }
 
+// legacyPinLevel 旧库 pinned（0/1，非零=全站置顶）映射到新置顶分级：板块置顶为本站新能力，旧数据无此语义
+func legacyPinLevel(v int) int {
+	if v > 0 {
+		return model.PinGlobal
+	}
+	return model.PinNone
+}
+
 type legacyCommentRow struct {
 	ID        uint           `gorm:"primaryKey"`
 	PostID    uint           `gorm:"column:post_id"`
@@ -757,7 +765,7 @@ func (s *LegacyImportService) importPosts(oldDB *gorm.DB, boardMap map[uint]uint
 			Content:     content,
 			Tags:        p.Tags,
 			PostType:    model.NormalizePostType(p.PostType), // question→question，normal→discussion
-			Pinned:      p.Pinned,
+			Pinned:      legacyPinLevel(p.Pinned),
 			Recommended: p.Featured,
 			Status:      model.ContentStatusPublished,
 			LikeCount:   p.LikeCount,