feat(backend): Webhooks mit HMAC-signierter Auslieferung (Modul 28)

WebhooksModule (WebhookSubscription: URL, Events, Secret, aktiv) mit
Event-Dispatcher, angehaengt an 10 Ereignisse in 8 bestehenden Services
(colony.created, inspection.created, queen.created, queen.replaced,
harvest.created, batch.created, batch.updated, product.stock_changed,
task.created, task.completed). Auslieferung ist best-effort und blockiert
die ausloesende Anfrage nicht bei Fehlern.

ApiCore-Backend/src/webhooks/webhook-events.ts

@@ -0,0 +1,14 @@
+export const WEBHOOK_EVENTS = [
+  'colony.created',
+  'inspection.created',
+  'queen.created',
+  'queen.replaced',
+  'harvest.created',
+  'batch.created',
+  'batch.updated',
+  'product.stock_changed',
+  'task.created',
+  'task.completed',
+] as const;
+
+export type WebhookEvent = (typeof WEBHOOK_EVENTS)[number];