fix: 文件不存在时提供报错信息

getFileUrlLogic 捕获 S3 NotFound 返回语义明确的错误信息，
getFileLogic 将 gRPC 错误转为普通 error 避免 HTTP 500。

app/objectstory/api/internal/logic/file/getFileLogic.go

@@ -14,6 +14,7 @@ import (
 	"juwan-backend/common/utils/contextj"
 
 	"github.com/zeromicro/go-zero/core/logx"
+	"google.golang.org/grpc/status"
 )
 
 type GetFileLogic struct {
@@ -46,7 +47,7 @@ func (l *GetFileLogic) GetFile(req *types.GetFileReq) (string, error) {
 		UserId: strconv.FormatInt(userID, 10),
 	})
 	if err != nil {
-		return "", err
+		return "", errors.New(status.Convert(err).Message())
 	}
 	if rpcResp.GetUrl() == "" {
 		return "", errors.New("file url is empty")

app/objectstory/rpc/internal/logic/getFileUrlLogic.go

@@ -9,6 +9,7 @@ import (
 	"juwan-backend/app/objectstory/rpc/pb"
 
 	"github.com/aws/aws-sdk-go-v2/service/s3"
+	s3types "github.com/aws/aws-sdk-go-v2/service/s3/types"
 	"github.com/zeromicro/go-zero/core/logx"
 )
 
@@ -37,6 +38,10 @@ func (l *GetFileUrlLogic) GetFileUrl(in *pb.GetFileUrlReq) (*pb.GetFileUrlResp,
 		Key:    &in.FileId,
 	})
 	if err != nil {
+		var nf *s3types.NotFound
+		if errors.As(err, &nf) {
+			return nil, errors.New("file not found")
+		}
 		return nil, err
 	}