feat: add settlement_type to SalesInvoice model and related DTOs

- Added settlement_type field to SalesInvoice model with ENUM values (CASH, CREDIT, MIXED).
- Updated SalesInvoice aggregate types, input types, and where filters to include settlement_type.
- Modified StatisticsService to calculate credit amounts based on settlement_type.
- Enhanced TspProviderOriginalSendPayloadDto to include settlement_type.
- Updated NamaProvider DTOs and utility functions to handle new settlement_type logic.
- Created migration to add settlement_type column to sales_invoices table and backfill existing records.

prisma/schema/shared/enum.prisma

@@ -157,6 +157,12 @@ enum ConsumerType {
   LEGAL
 }
 
+enum InvoiceSettlementType {
+  CASH
+  CREDIT
+  MIXED
+}
+
 enum TspProviderType {
   NAMA
   SUN