feat(server): say at startup when alerting is unconfigured (#107) WARN once at startup when BRAIN_NTFY_URL is unset, naming what will not fire (brain_edit_root governance rewrites, capture audit degradation). Rebase of PR #108 (never CI-tested) onto current main, no functional change to alertingWarnings. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Co-authored-by: Mathias <mthbqv@gmail.com>