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/test-utils/reset-db.ts

@@ -8,7 +8,7 @@ import type { PrismaClient } from '@prisma/client';
 export async function resetDb(prisma: PrismaClient): Promise<void> {
   await prisma.$executeRawUnsafe(
     `TRUNCATE TABLE
-      "IiosComplianceHold","IiosProjectionCursor","IiosIdempotencyCommand","IiosDlqItem","IiosAuditLink",
+      "IiosRetentionPolicySnapshot","IiosComplianceHold","IiosProjectionCursor","IiosIdempotencyCommand","IiosDlqItem","IiosAuditLink",
       "IiosMeetingActionItem","IiosActionItem","IiosTranscriptSegment","IiosMeetingTranscript","IiosMeetingSummary","IiosMeetingParticipant","IiosMeeting","IiosMeetingRequest",
       "IiosCalendarSyncCursor","IiosCalendarEvent","IiosCalendarProviderAccount","IiosAvailabilityWindow",
       "IiosAiEvidenceLink","IiosAiClaim","IiosAiToolCall","IiosAiArtifact","IiosAiModelRun","IiosAiJob","IiosEmbeddingRef",