feat(skills): 技能库 - 内置技能目录迁移为 Markdown 包

backend/internal/database/schema.go

@@ -65,9 +65,11 @@ func Models() []any {
 		&model.StorageLocation{},
 		&model.UserDailyUploadUsage{},
 		&model.Skill{},
+		&model.SkillLibraryCategory{},
 		&model.SkillVersion{},
 		&model.SkillFile{},
 		&model.UserSkillState{},
+		&model.BuiltinSkillTombstone{},
 		&model.Tool{},
 		&model.ToolFavorite{},
 		&model.Resource{},