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/main.py

@@ -37,6 +37,7 @@ from app.routers import professional_reports as professional_reports_router
 from app.routers import analytics as analytics_router
 from app.routers import advanced_metrics as advanced_metrics_router
 from app.routers import osint as osint_router
+from app.routers import webhooks as webhooks_router
 from app.domain.errors import DomainError
 from app.middleware.error_handler import domain_exception_handler
 from app.middleware.request_context import RequestContextMiddleware
@@ -123,6 +124,7 @@ app.include_router(professional_reports_router.router, prefix="/api/v1")
 app.include_router(analytics_router.router, prefix="/api/v1")
 app.include_router(advanced_metrics_router.router, prefix="/api/v1")
 app.include_router(osint_router.router, prefix="/api/v1")
+app.include_router(webhooks_router.router, prefix="/api/v1")
 
 
 @app.get("/health", include_in_schema=False)