refactor: GetOverview 5 次独立查询合并为单次 GROUP BY

- 新增 PostRepo.GetOverviewByUserID 单次 CASE WHEN + GROUP BY 查询
- Service 层 GetOverview 从 5 次 DB 查询减少为 1 次
- 接口 postStore 新增 GetOverviewByUserID 声明

internal/service/post_service.go

@@ -187,18 +187,12 @@ type StudioOverview struct {
 	RejectedCount int64 `json:"rejected_count"`
 }
 
-// GetOverview 获取创作中心数据概览
+// GetOverview 获取创作中心数据概览（单次 GROUP BY 查询）
 func (s *PostService) GetOverview(userID uint) (*StudioOverview, error) {
-	// 获取各状态文章数量（分页传 1 条只取 total）
-	_, totalPosts, err := s.repo.FindByUserIDAndStatus(userID, "", 0, 1)
+	totalPosts, draftCount, pendingCount, approvedCount, rejectedCount, err := s.repo.GetOverviewByUserID(userID)
 	if err != nil {
 		return nil, err
 	}
-	_, draftCount, _ := s.repo.FindByUserIDAndStatus(userID, model.PostStatusDraft, 0, 1)
-	_, pendingCount, _ := s.repo.FindByUserIDAndStatus(userID, model.PostStatusPending, 0, 1)
-	_, approvedCount, _ := s.repo.FindByUserIDAndStatus(userID, model.PostStatusApproved, 0, 1)
-	_, rejectedCount, _ := s.repo.FindByUserIDAndStatus(userID, model.PostStatusRejected, 0, 1)
-
 	return &StudioOverview{
 		TotalPosts:    totalPosts,
 		DraftCount:    draftCount,

internal/service/repository.go

@@ -37,6 +37,7 @@ type postStore interface {
 	FindPageable(keyword string, offset, limit int) ([]model.Post, int64, error)
 	FindAdminPageable(keyword, status string, offset, limit int) ([]model.Post, int64, error)
 	FindByUserIDAndStatus(userID uint, status string, offset, limit int) ([]model.Post, int64, error)
+	GetOverviewByUserID(userID uint) (totalPosts, draftCount, pendingCount, approvedCount, rejectedCount int64, err error)
 	FindPendingRevisions(keyword string, offset, limit int) ([]model.Post, int64, error)
 	Update(post *model.Post) error
 	SoftDelete(id uint) error