feat(posts): add preview URL fields for post images

Add PreviewURL and PreviewURLLarge fields to PostImage model and responses. Image data now supports format "url|preview_url|preview_url_large" for storing multiple image variants. Also change comment cursor pagination to sort by created_at ASC (oldest first) to display earliest comments as first floor, and make AdminReviewVerificationRequest.Approve field optional.

internal/dto/dto.go

@@ -1404,7 +1404,7 @@ type AdminVerificationDetailResponse struct {
 
 // AdminReviewVerificationRequest 管理端审核认证请求
 type AdminReviewVerificationRequest struct {
-	Approve      bool   `json:"approve" binding:"required"`
+	Approve      bool   `json:"approve"`
 	RejectReason string `json:"reject_reason" binding:"omitempty,max=500"`
 }
 

internal/dto/post_converter.go

@@ -17,6 +17,8 @@ func ConvertPostImageToResponse(img *model.PostImage) PostImageResponse {
 		ID:              img.ID,
 		URL:             img.URL,
 		ThumbnailURL:    img.ThumbnailURL,
+		PreviewURL:      img.PreviewURL,
+		PreviewURLLarge: img.PreviewURLLarge,
 		Width:           img.Width,
 		Height:          img.Height,
 	}

internal/repository/comment_repo.go

@@ -495,14 +495,14 @@ func (r *commentRepository) GetCommentsByPostIDForAdmin(postID string, page, pag
 // ========== Cursor Pagination Methods ==========
 
 // GetCommentsByCursor 游标分页获取帖子评论（包含回复）
-// 排序方式：created_at DESC
+// 排序方式：created_at ASC（最早发布的为一楼）
 func (r *commentRepository) GetCommentsByCursor(ctx context.Context, postID string, req *cursor.PageRequest) (*cursor.CursorPageResult[*model.Comment], error) {
 	// 构建基础查询 - 只查询顶级评论
 	query := r.db.WithContext(ctx).Model(&model.Comment{}).
 		Where("post_id = ? AND parent_id IS NULL AND status = ?", postID, model.CommentStatusPublished)
 
 	// 使用游标构建器
-	builder := cursor.NewBuilder(query, cursor.SortByCreatedAtDesc).
+	builder := cursor.NewBuilder(query, cursor.SortByCreatedAtAsc).
 		WithCursor(req.Cursor, req.Direction).
 		WithPageSize(req.PageSize)
 
@@ -539,7 +539,7 @@ func (r *commentRepository) GetCommentsByCursor(ctx context.Context, postID stri
 			nextCursor = cursor.NewCursor(
 				cursor.FormatTime(lastComment.CreatedAt),
 				lastComment.ID,
-				cursor.SortByCreatedAtDesc,
+				cursor.SortByCreatedAtAsc,
 			).Encode()
 		}
 		// 上一页游标
@@ -547,7 +547,7 @@ func (r *commentRepository) GetCommentsByCursor(ctx context.Context, postID stri
 		prevCursor = cursor.NewCursor(
 			cursor.FormatTime(firstComment.CreatedAt),
 			firstComment.ID,
-			cursor.SortByCreatedAtDesc,
+			cursor.SortByCreatedAtAsc,
 		).Encode()
 	}
 

internal/repository/post_repo.go

@@ -148,10 +148,21 @@ func (r *postRepository) UpdateWithImages(post *model.Post, images *[]string) er
 			return err
 		}
 
-		for i, url := range *images {
+		for i, imageData := range *images {
+			parts := strings.Split(imageData, "|")
+			url := parts[0]
+			var previewURL, previewURLLarge string
+			if len(parts) >= 2 && parts[1] != "" {
+				previewURL = parts[1]
+			}
+			if len(parts) >= 3 && parts[2] != "" {
+				previewURLLarge = parts[2]
+			}
 			image := &model.PostImage{
 				PostID:          post.ID,
 				URL:             url,
+				PreviewURL:      previewURL,
+				PreviewURLLarge: previewURLLarge,
 				SortOrder:       i,
 			}
 			if err := tx.Create(image).Error; err != nil {
@@ -695,10 +706,22 @@ func (r *postRepository) createWithTx(tx *gorm.DB, post *model.Post, images []st
 	}
 
 	// 创建图片记录
-	for i, url := range images {
+	// 支持格式：["url", "url|preview_url|preview_url_large", ...]
+	for i, imageData := range images {
+		parts := strings.Split(imageData, "|")
+		url := parts[0]
+		var previewURL, previewURLLarge string
+		if len(parts) >= 2 && parts[1] != "" {
+			previewURL = parts[1]
+		}
+		if len(parts) >= 3 && parts[2] != "" {
+			previewURLLarge = parts[2]
+		}
 		image := &model.PostImage{
 			PostID:          post.ID,
 			URL:             url,
+			PreviewURL:      previewURL,
+			PreviewURLLarge: previewURLLarge,
 			SortOrder:       i,
 		}
 		if err := tx.Create(image).Error; err != nil {

internal/service/admin_post_service.go

@@ -259,6 +259,8 @@ func convertPostToAdminListResponse(post *model.Post) dto.AdminPostListResponse
 			ID:              img.ID,
 			URL:             img.URL,
 			ThumbnailURL:    img.ThumbnailURL,
+			PreviewURL:      img.PreviewURL,
+			PreviewURLLarge: img.PreviewURLLarge,
 			Width:           img.Width,
 			Height:          img.Height,
 		}
@@ -301,6 +303,8 @@ func convertPostToAdminDetailResponse(post *model.Post) *dto.AdminPostDetailResp
 			ID:              img.ID,
 			URL:             img.URL,
 			ThumbnailURL:    img.ThumbnailURL,
+			PreviewURL:      img.PreviewURL,
+			PreviewURLLarge: img.PreviewURLLarge,
 			Width:           img.Width,
 			Height:          img.Height,
 		}