perf: batch gateway submits and isolate callbacks

api/prisma/migrations/20260825103000_add_gateway_submit_outbox/migration.sql

@@ -0,0 +1,29 @@
+CREATE TABLE "GatewaySubmitOutbox" (
+    "id" TEXT NOT NULL,
+    "submitId" TEXT NOT NULL,
+    "messageRecordId" TEXT NOT NULL,
+    "channelId" TEXT NOT NULL,
+    "payload" JSONB NOT NULL,
+    "schemaVersion" TEXT NOT NULL DEFAULT 'v1',
+    "status" TEXT NOT NULL DEFAULT 'pending',
+    "attemptCount" INTEGER NOT NULL DEFAULT 0,
+    "nextAttemptAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "leaseOwner" TEXT,
+    "leaseExpiresAt" TIMESTAMP(3),
+    "streamEntryId" TEXT,
+    "publishedAt" TIMESTAMP(3),
+    "lastError" TEXT,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "GatewaySubmitOutbox_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX "GatewaySubmitOutbox_submitId_key"
+ON "GatewaySubmitOutbox"("submitId");
+
+CREATE INDEX "GatewaySubmitOutbox_pending_claim_idx"
+ON "GatewaySubmitOutbox"("nextAttemptAt", "createdAt")
+WHERE "status" IN ('pending', 'publishing');
+
+CREATE INDEX "GatewaySubmitOutbox_messageRecordId_idx"
+ON "GatewaySubmitOutbox"("messageRecordId");

api/prisma/schema.prisma

@@ -1828,6 +1828,28 @@ model SmsSubmitRecord {
   @@index([channelGroupId])
 }
 
+model GatewaySubmitOutbox {
+  id              String    @id @default(cuid())
+  submitId        String    @unique
+  messageRecordId String
+  channelId       String
+  payload         Json
+  schemaVersion   String    @default("v1")
+  status          String    @default("pending")
+  attemptCount    Int       @default(0)
+  nextAttemptAt   DateTime  @default(now())
+  leaseOwner      String?
+  leaseExpiresAt  DateTime?
+  streamEntryId   String?
+  publishedAt     DateTime?
+  lastError       String?
+  createdAt       DateTime  @default(now())
+  updatedAt       DateTime  @updatedAt
+
+  @@index([submitId, status])
+  @@index([messageRecordId])
+}
+
 model DailyReconciliationReport {
   id              String   @id @default(cuid())
   reportDate      DateTime @db.Date