feat(service): P2.2 MessageService — native send + receipts/unread + traceId

openThread (create-or-join), send (idempotent, bumps other participants' unread,
message.sent outbox event, traceId DB->event), markRead (READ receipt + unread
reset), contentRef attachment placeholder. Adds messageSent to contracts events.
5 DB-backed tests green; 24 total.

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

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

@@ -4,10 +4,11 @@ import { PlatformModule } from './platform/platform.module';
 import { InteractionsModule } from './interactions/interactions.module';
 import { OutboxModule } from './outbox/outbox.module';
 import { ThreadsModule } from './threads/threads.module';
+import { MessageModule } from './messaging/message.module';
 import { HealthController } from './health.controller';
 
 @Module({
-  imports: [PrismaModule, PlatformModule, InteractionsModule, OutboxModule, ThreadsModule],
+  imports: [PrismaModule, PlatformModule, InteractionsModule, OutboxModule, ThreadsModule, MessageModule],
   controllers: [HealthController],
 })
 export class AppModule {}