feat(ancpi): batch ordering + download existing orders

Major rewrite:
- Queue now processes batches: addToCart×N → saveMetadata×N → ONE
  submitOrder → poll → download ALL documents → store in MinIO
- Removed unique constraint on orderId (shared across batch items)
- Added step=download to test endpoint: downloads PDFs from 5
  existing orders (9685480-9685484) and stores in MinIO
- step=order now uses enqueueBatch for 2 test parcels (61904, 309952)
  as ONE ePay order instead of separate orders

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

prisma/schema.prisma

@@ -120,7 +120,7 @@ model RegistryAudit {
 
 model CfExtract {
   id              String    @id @default(uuid())
-  orderId         String?   @unique          // ePay orderId
+  orderId         String?                     // ePay orderId (shared across batch items)
   basketRowId     Int?                        // ePay cart item ID
   nrCadastral     String                      // cadastral number
   nrCF            String?                     // CF number if different