Add transactional emails (SMTP) and planner features (no-go areas, notes, crash recovery)

Transactional emails:
- Add nodemailer SMTP email module with dev-mode console logging
- Magic link template and welcome template with HTML + plain text
- Wire sendMagicLink into login flow, sendWelcome into registration
- Update privacy page and deploy docs for SMTP configuration

Planner features:
- No-go areas: draw polygons on map (leaflet-geoman), synced via Yjs,
  passed to BRouter as nogos parameter, route recomputes on change
- Session notes: collaborative Y.Text textarea in sidebar tab
- Crash recovery: periodic localStorage save of Yjs state, restore on reconnect
- Rate limit session creation (10/IP/hour) in /new route

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infrastructure/docker-compose.yml

@@ -27,6 +27,8 @@ services:
       NODE_ENV: production
       PORT: 3000
       SENTRY_RELEASE: ${SENTRY_RELEASE:-}
+      SMTP_URL: ${SMTP_URL:-}
+      SMTP_FROM: ${SMTP_FROM:-trails.cool <noreply@trails.cool>}
     depends_on:
       postgres:
         condition: service_healthy