feat: restore report files and export claim amounts

tests/apps/exchange/test_api.py

@@ -316,6 +316,7 @@ def build_exchange_payload() -> dict[str, list[dict[str, object]]]:
                 "party_role": "ответчик",
                 "status": "in_progress",
                 "decision_date": "2026-03-25",
+                "claim_amount": "1250000.50",
             }
         ],
         "bankruptcy_procedures": [
@@ -463,6 +464,10 @@ class ExchangePackageApiTest(APITestCase):
         self.assertEqual(FinancialReport.objects.count(), 1)
         self.assertEqual(FinancialReportLine.objects.count(), 1)
         self.assertEqual(ArbitrationCase.objects.count(), 1)
+        self.assertEqual(
+            ArbitrationCase.objects.get().claim_amount,
+            Decimal("1250000.50"),
+        )
         self.assertEqual(BankruptcyProcedure.objects.count(), 1)
         self.assertEqual(
             BankruptcyProcedure._meta.get_field("status").max_length,