feat(iios): retention_policy_snapshot + sweep (archive→redact, hold-aware) (P9)

Adds IiosRetentionPolicySnapshot (per-interaction frozen lifecycle timestamps)
+ IiosInteraction.dataClass, and a RetentionService whose sweep captures
snapshots then archives (status change) and, past delete_after, redacts content
in place (reusing the Slice-8 tombstone) — never a hard delete. An active
compliance hold blocks both; every action is audited and tenant-scopeable.

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

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

@@ -16,6 +16,7 @@ import { AiModule } from './ai/ai.module';
 import { CalendarModule } from './calendar/calendar.module';
 import { CapabilityModule } from './capability/capability.module';
 import { DsrModule } from './dsr/dsr.module';
+import { RetentionModule } from './retention/retention.module';
 import { HealthController } from './health.controller';
 import { MetricsController } from './observability/metrics.controller';
 import { DevController } from './dev/dev.controller';
@@ -39,6 +40,7 @@ import { DevController } from './dev/dev.controller';
     CalendarModule,
     CapabilityModule,
     DsrModule,
+    RetentionModule,
   ],
   controllers: [HealthController, MetricsController, DevController],
 })