feat: harden sessions and track downstream acknowledgements

api/prisma/schema.prisma

@@ -360,6 +360,8 @@ model SmsApplication {
   queuePriority         String   @default("normal")
   maxPhonesPerTask      Int      @default(1000000)
   templateMismatchMode  String   @default("reject")
+  downstreamReceiptRetryEnabled Boolean @default(true)
+  downstreamUplinkRetryEnabled  Boolean @default(true)
   status                String   @default("active")
   createdAt             DateTime @default(now())
   updatedAt             DateTime @updatedAt
@@ -1188,8 +1190,16 @@ model CmppDownstreamDelivery {
   deliveryType    String
   status          String   @default("pending")
   payload         Json
+  retryEnabled    Boolean  @default(true)
   retryCount      Int      @default(0)
   nextRetryAt     DateTime?
+  sentAt          DateTime?
+  acknowledgedAt  DateTime?
+  ackDeadlineAt   DateTime?
+  ackResult       Int?
+  ackSequenceId   String?
+  ackMessageId    String?
+  connectionId    String?
   deliveredAt     DateTime?
   lastError       String?
   createdAt       DateTime @default(now())
@@ -1204,6 +1214,7 @@ model CmppDownstreamDelivery {
   @@index([messageId])
   @@index([messageRecordId])
   @@index([deliveryType, status])
+  @@index([status, ackDeadlineAt])
 }
 
 model GatewaySubmitDeadLetter {