v0.2.0

Makes the stack operable, not just runnable: authentication, self-monitoring,
alert delivery, backups, and infrastructure as code.

Added

• Authenticated ingestion: OTLP now requires a bearer token
  (OTLP_AUTH_TOKEN).
• Self-monitoring: node-exporter, a Stack Health dashboard, and a
  disk-space alert that backstops Loki and Tempo (neither can cap its own
  size).
• Alert delivery: Alertmanager posts to any webhook
  (ALERT_WEBHOOK_URL), and an always-firing Watchdog pings a dead man's
  switch (HEARTBEAT_URL) so even a dead host gets noticed.
• Backup and restore: just backup / just restore, tested by wiping
  every volume and recovering.
• The Cloudflare edge as code: infra/ (OpenTofu) manages the tunnel,
  DNS, and an email-PIN Access policy in front of Grafana.
• Operator and onboarding docs: a runbook plus copy-paste telemetry
  templates for new projects.
• Logs Overview dashboard for OTLP logs, an Active Alerts table on Stack
  Health, and Stack Health as the Grafana home page.

Changed

• Prometheus storage is now capped by size as well as time (15 GB).
• Tempo upgraded to 3.0, migrating off the removed ingester/compactor
  config and verified in place against live traffic.