Do not use lower tag names to find releases/tags (#29261)

Fix #26090, see
https://github.com/go-gitea/gitea/issues/26090#issuecomment-1952013206

Since `TagName` stores the original tag name and `LowerTagName` stores
the lower tag name, it doesn't make sense to use lowercase tags as
`TagNames` in `FindReleasesOptions`.

https://github.com/go-gitea/gitea/blob/5e72526da4e915791f03af056890e16821bde052/services/repository/push.go#L396-L397

While the only other usage looks correct:

https://github.com/go-gitea/gitea/blob/5e72526da4e915791f03af056890e16821bde052/routers/web/repo/repo.go#L416
(cherry picked from commit 0ea8de2d0729e1e1d0ea9de1e59fbcb673e87fd2)

services/repository/push.go

@@ -321,14 +321,9 @@ func pushUpdateAddTags(ctx context.Context, repo *repo_model.Repository, gitRepo
 		return nil
 	}
 
-	lowerTags := make([]string, 0, len(tags))
-	for _, tag := range tags {
-		lowerTags = append(lowerTags, strings.ToLower(tag))
-	}
-
 	releases, err := db.Find[repo_model.Release](ctx, repo_model.FindReleasesOptions{
 		RepoID:   repo.ID,
-		TagNames: lowerTags,
+		TagNames: tags,
 	})
 	if err != nil {
 		return fmt.Errorf("db.Find[repo_model.Release]: %w", err)
@@ -338,6 +333,11 @@ func pushUpdateAddTags(ctx context.Context, repo *repo_model.Repository, gitRepo
 		relMap[rel.LowerTagName] = rel
 	}
 
+	lowerTags := make([]string, 0, len(tags))
+	for _, tag := range tags {
+		lowerTags = append(lowerTags, strings.ToLower(tag))
+	}
+
 	newReleases := make([]*repo_model.Release, 0, len(lowerTags)-len(relMap))
 
 	emailToUser := make(map[string]*user_model.User)