claude.ai connectors call the server with no Authorization header (confirmed
via request logging). Add a configurable default Gitea PAT so unauthenticated
clients (like claude.ai) can still reach the server.
Claude Code continues to pass per-request PATs; defaultToken="" preserves
the existing strict behaviour when the env var is unset.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>