Refactor blog post logic to standardize field names and improve error handling; implement pagination for post listing and add tag retrieval functionality.

app/internal/logic/downloadpresignedurllogic.go

@@ -37,7 +37,7 @@ func (l *DownloadPresignedURLLogic) DownloadPresignedURL(req *types.DownloadPres
 	// Generate presigned GET URL
 	getObjectInput := &s3.GetObjectInput{
 		Bucket: &l.svcCtx.Config.S3.Bucket,
-		Key:    &req.File_key,
+		Key:    &req.FileKey,
 	}
 
 	presignedReq, err := presignClient.PresignGetObject(l.ctx, getObjectInput, func(opts *s3.PresignOptions) {
@@ -49,7 +49,7 @@ func (l *DownloadPresignedURLLogic) DownloadPresignedURL(req *types.DownloadPres
 	}
 
 	return &types.DownloadPresignedURLResp{
-		Url:       presignedReq.URL,
-		Expire_at: expireAt,
+		Url:      presignedReq.URL,
+		ExpireAt: expireAt,
 	}, nil
 }