fix(worker): start with a repository-only token

The start-up check read the token's account with GET /user, which needs the
read:user scope. A token with only repository scope, which is all the worker
needs, got 403 and the worker exited in a restart loop. On 403 it now
names the commit author from BOT_NAME (default gbr-bot) and still checks
push access on the games repo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/worker.go

@@ -60,7 +60,12 @@ func (c *workerConfig) checkBot() error {
 		Email string `json:"email"`
 	}
 	if err := c.giteaGet("/user", &user); err != nil {
-		return fmt.Errorf("GITEA_TOKEN: %w", err)
+		if !strings.HasPrefix(err.Error(), "HTTP 403") {
+			return fmt.Errorf("GITEA_TOKEN: %w", err)
+		}
+		// A repository-only token (all the worker needs) may not read its own account: name the author from
+		// BOT_NAME instead. Whether it can push is still checked below.
+		user.Login = envOr("BOT_NAME", "gbr-bot")
 	}
 	var repo struct {
 		Permissions struct {