feat(service): ingest endpoint with kernel gates (P1.4)

POST /v1/interactions/ingest: fail-closed OPA gate -> resolve scope/handle(MDM,
no silent merge)/actor/channel/thread -> idempotent write of interaction+parts+
outbox CloudEvent in one tx. 4 DB-backed gate tests green (idempotent /
fail-closed / unresolved-handle / outbox event). 16 tests total.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/src/app.module.ts

@@ -1,10 +1,11 @@
 import { Module } from '@nestjs/common';
 import { PrismaModule } from './prisma/prisma.module';
 import { PlatformModule } from './platform/platform.module';
+import { InteractionsModule } from './interactions/interactions.module';
 import { HealthController } from './health.controller';
 
 @Module({
-  imports: [PrismaModule, PlatformModule],
+  imports: [PrismaModule, PlatformModule, InteractionsModule],
   controllers: [HealthController],
 })
 export class AppModule {}