feat: complete signature and drainage reporting workflows

api/prisma/schema.prisma

@@ -720,6 +720,8 @@ model ChannelSignatureReportTask {
   tenantId    String
   signatureId String
   channelId   String
+  reportType  String   @default("signature")
+  drainageItemId String?
   status      String   @default("pending")
   reason      String?
   createdById String?
@@ -734,6 +736,8 @@ model ChannelSignatureReportTask {
 
   @@index([tenantId, status])
   @@index([signatureId, channelId])
+  @@index([signatureId, drainageItemId, channelId])
+  @@index([reportType, status])
 }
 
 model ChannelSignatureReportRecord {