Switch SMS billing to credit units with IRT top-ups.

Balance is SMS credits (1 per 64 chars); top-ups add floor(IRT/500) credits, track sms_sent_count, and convert existing IRT balances.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/customers/customers.service.ts

@@ -908,7 +908,11 @@ export class CustomersService {
         });
         totalCost += cost;
       }
-      charged = await this.smsBilling.chargeAmount(businessId, totalCost);
+      charged = await this.smsBilling.chargeAmount(
+        businessId,
+        totalCost,
+        personalizedPayloads.length,
+      );
     }
 
     try {
@@ -940,10 +944,13 @@ export class CustomersService {
           );
           serverIds.push(result.serverId);
         } catch (err) {
-          const refundAmount = personalizedPayloads
-            .slice(i)
-            .reduce((sum, item) => sum + item.cost, 0);
-          await this.smsBilling.refund(businessId, refundAmount);
+          const remaining = personalizedPayloads.slice(i);
+          const refundAmount = remaining.reduce((sum, item) => sum + item.cost, 0);
+          await this.smsBilling.refund(
+            businessId,
+            refundAmount,
+            remaining.length,
+          );
           charged = 0;
           throw err;
         }
@@ -960,7 +967,11 @@ export class CustomersService {
       };
     } catch (err) {
       if (charged > 0) {
-        await this.smsBilling.refund(businessId, charged);
+        await this.smsBilling.refund(
+          businessId,
+          charged,
+          personalized ? personalizedPayloads.length : recipients.length,
+        );
       }
       if (
         err instanceof BadRequestException ||