Add tier-based scan scheduler and webhook triggers (FRE-4498)

- ScanScheduler: tier-based scheduling (BASIC=24h, PLUS=6h, PREMIUM=1h)
- WebhookHandler: HMAC-verified webhook ingestion with SCAN_TRIGGER support
- API routes: /scheduler and /webhooks endpoints under /api/v1/darkwatch
- Jobs: scheduled scan checker + webhook retry processor via BullMQ
- Schema: ScanSchedule, WebhookEvent models; ScanJob.scheduledBy field
- Types: ScheduleStatus, WebhookEventType, WebhookTriggerInput
- Tests: scheduler lifecycle + webhook signature/processing tests

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/api/src/routes/index.ts

@@ -6,11 +6,15 @@ export function darkwatchRoutes(fastify: FastifyInstance) {
     const exposures = (await import("./exposure.routes")).exposureRoutes;
     const alerts = (await import("./alert.routes")).alertRoutes;
     const scans = (await import("./scan.routes")).scanRoutes;
+    const scheduler = (await import("./scheduler.routes")).schedulerRoutes;
+    const webhooks = (await import("./webhook.routes")).webhookRoutes;
 
     root.register(watchlist, { prefix: "/watchlist" });
     root.register(exposures, { prefix: "/exposures" });
     root.register(alerts, { prefix: "/alerts" });
     root.register(scans, { prefix: "/scan" });
+    root.register(scheduler, { prefix: "/scheduler" });
+    root.register(webhooks, { prefix: "/webhooks" });
   }, { prefix: "/api/v1/darkwatch" });
 }