feat(phases): implement webhooks (6.1), email (7.1), user preferences (7.2)

- Phase 6.1: WebhookConfig model, CRUD router (/api/v1/webhooks, admin-only),
  dispatch_webhook() with HMAC signing; integrated into test validation,
  campaign completion, and MITRE sync job
- Phase 7.1: SMTP email service with send_test_validated_email,
  send_campaign_completed_email, send_new_mitre_techniques_email;
  notify_role_with_email() added to notification_service
- Phase 7.2: notification_preferences and jira_account_id on User model;
  PATCH /users/me/preferences endpoint; Alembic migrations b031phase6 and b032phase7

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

backend/app/routers/campaigns.py

@@ -33,6 +33,7 @@ from app.services.campaign_crud_service import (
 from app.domain.unit_of_work import UnitOfWork
 from app.services.audit_service import log_action
 from app.services.notification_service import notify_role
+from app.services.webhook_service import dispatch_webhook
 
 logger = logging.getLogger(__name__)
 
@@ -284,6 +285,7 @@ def complete_campaign(
         )
         uow.commit()
     db.refresh(campaign)
+    dispatch_webhook("campaign.completed", {"campaign_id": str(campaign.id), "name": campaign.name})
 
     return serialize_campaign(db, campaign)