feat: add email notification system (Brevo SMTP + N8N daily digest)

- Add core notification service: types, email-service (nodemailer/Brevo SMTP), notification-service (digest builder, preference CRUD, HTML renderer)
- Add API routes: POST /api/notifications/digest (N8N cron, Bearer auth), GET/PUT /api/notifications/preferences (session auth)
- Add NotificationPreferences UI component (Bell button + dialog with per-type toggles) in Registratura toolbar
- Add 7 Brevo SMTP env vars to docker-compose.yml
- Update CLAUDE.md, ROADMAP.md, DATA-MODEL.md, SYSTEM-ARCHITECTURE.md, CONFIGURATION.md, DOCKER-DEPLOYMENT.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -22,6 +22,7 @@
     "next": "16.1.6",
     "next-auth": "^4.24.13",
     "next-themes": "^0.4.6",
+    "nodemailer": "^7.0.13",
     "proj4": "^2.20.3",
     "qrcode": "^1.5.4",
     "radix-ui": "^1.4.3",
@@ -37,6 +38,7 @@
     "@tailwindcss/postcss": "^4",
     "@types/jszip": "^3.4.0",
     "@types/node": "^20",
+    "@types/nodemailer": "^7.0.11",
     "@types/proj4": "^2.5.6",
     "@types/qrcode": "^1.5.6",
     "@types/react": "^19",