feat: Enhance currency handling and validation across scenarios

- Updated form template to prefill currency input with default value and added help text for clarity.
- Modified integration tests to assert more descriptive error messages for invalid currency codes.
- Introduced new tests for currency normalization and validation in various scenarios, including imports and exports.
- Added comprehensive tests for pricing calculations, ensuring defaults are respected and overrides function correctly.
- Implemented unit tests for pricing settings repository, ensuring CRUD operations and default settings are handled properly.
- Enhanced scenario pricing evaluation tests to validate currency handling and metadata defaults.
- Added simulation tests to ensure Monte Carlo runs are accurate and handle various distribution scenarios.

tests/test_export_routes.py

@@ -128,3 +128,17 @@ def test_scenario_export_excel(client: TestClient, unit_of_work_factory) -> None
 
     with ZipFile(BytesIO(response.content)) as archive:
         assert "xl/workbook.xml" in archive.namelist()
+
+
+def test_scenario_export_rejects_invalid_currency_filter(client: TestClient) -> None:
+    response = client.post(
+        "/exports/scenarios",
+        json={
+            "format": "csv",
+            "filters": {"currencies": ["USD", "XX"]},
+        },
+    )
+
+    assert response.status_code == 422
+    detail = response.json()["detail"]
+    assert "Invalid currency code" in detail