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/prisma/migrations/20260703070438_retention_sweep/migration.sql

@@ -0,0 +1,29 @@
+-- AlterTable
+ALTER TABLE "IiosInteraction" ADD COLUMN     "dataClass" TEXT NOT NULL DEFAULT 'internal';
+
+-- CreateTable
+CREATE TABLE "IiosRetentionPolicySnapshot" (
+    "id" TEXT NOT NULL,
+    "policyKey" TEXT NOT NULL,
+    "scopeSnapshotId" TEXT NOT NULL,
+    "targetType" TEXT NOT NULL,
+    "targetId" TEXT NOT NULL,
+    "dataClass" TEXT NOT NULL,
+    "retainUntil" TIMESTAMP(3),
+    "archiveAfter" TIMESTAMP(3) NOT NULL,
+    "deleteAfter" TIMESTAMP(3) NOT NULL,
+    "sourceVersion" TEXT NOT NULL DEFAULT 'v1',
+    "status" TEXT NOT NULL DEFAULT 'ACTIVE',
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "IiosRetentionPolicySnapshot_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "IiosRetentionPolicySnapshot_status_deleteAfter_idx" ON "IiosRetentionPolicySnapshot"("status", "deleteAfter");
+
+-- CreateIndex
+CREATE INDEX "IiosRetentionPolicySnapshot_scopeSnapshotId_status_idx" ON "IiosRetentionPolicySnapshot"("scopeSnapshotId", "status");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "IiosRetentionPolicySnapshot_targetType_targetId_key" ON "IiosRetentionPolicySnapshot"("targetType", "targetId");