feat(p9): IiosDlqItem + DlqService (dead-letter + deterministic replay)

Task D.1: mandated dlq_item table (sourceType/sourceId/failureStage/errorCode/
retryCount/payloadRef/consumerName/scopeId/status). DlqService.record (idempotent
per consumer+sourceId, bumps retryCount), onConsumerFailure (quarantine + clear the
IiosProcessedEvent claim so it's replayable — fixes claim-then-fail), registerHandler
+ replay (clears claim, awaits the registered consumer handler → RESOLVED on success,
QUARANTINED+retry on repeat throw; outbox-sourced items reset to PENDING). Wired into
OutboxModule; resetDb truncates it. 3 tests.

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

packages/iios-service/prisma/migrations/20260702195657_dlq/migration.sql

@@ -0,0 +1,24 @@
+-- CreateTable
+CREATE TABLE "IiosDlqItem" (
+    "id" TEXT NOT NULL,
+    "sourceType" TEXT NOT NULL,
+    "sourceId" TEXT NOT NULL,
+    "failureStage" TEXT NOT NULL,
+    "errorCode" TEXT,
+    "retryCount" INTEGER NOT NULL DEFAULT 0,
+    "payloadRef" TEXT,
+    "consumerName" TEXT,
+    "scopeId" TEXT,
+    "status" TEXT NOT NULL DEFAULT 'QUARANTINED',
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "lastFailedAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "resolvedAt" TIMESTAMP(3),
+
+    CONSTRAINT "IiosDlqItem_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE INDEX "IiosDlqItem_scopeId_status_idx" ON "IiosDlqItem"("scopeId", "status");
+
+-- CreateIndex
+CREATE UNIQUE INDEX "IiosDlqItem_consumerName_sourceId_key" ON "IiosDlqItem"("consumerName", "sourceId");