fix(files): use absolute path everywhere

(cherry picked from commit 68636f27da707f3ee87ba0e4f1ff100504486608)

pkg/routes/api/v1/avatar.go

@@ -167,7 +167,7 @@ func UploadAvatar(c echo.Context) (err error) {
 	// Remove the old file if one exists
 	if u.AvatarFileID != 0 {
 		f := &files.File{ID: u.AvatarFileID}
-		if err := f.Delete(); err != nil {
+		if err := f.Delete(s); err != nil {
 			if !files.IsErrFileDoesNotExist(err) {
 				_ = s.Rollback()
 				return handler.HandleHTTPError(err)