fix architecture and write new tests

packages/database/prisma/migrations/20260609201000_add_webhook_events/migration.sql

@@ -0,0 +1,18 @@
+CREATE TABLE IF NOT EXISTS "webhook_events" (
+  "id" TEXT NOT NULL,
+  "provider" TEXT NOT NULL,
+  "providerEventId" TEXT NOT NULL,
+  "eventType" TEXT NOT NULL,
+  "status" TEXT NOT NULL,
+  "payloadHash" TEXT NOT NULL,
+  "errorMessage" TEXT,
+  "receivedAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  "processedAt" TIMESTAMP(3),
+  CONSTRAINT "webhook_events_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS "webhook_events_provider_providerEventId_key"
+  ON "webhook_events"("provider", "providerEventId");
+
+CREATE INDEX IF NOT EXISTS "webhook_events_provider_status_idx"
+  ON "webhook_events"("provider", "status");