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_import_api.py

@@ -68,3 +68,35 @@ def test_scenario_import_commit_invalid_token_returns_404(
     )
     assert response.status_code == 404
     assert "Unknown scenario import token" in response.json()["detail"]
+
+
+def test_scenario_import_preview_rejects_invalid_currency(
+    client: TestClient,
+    unit_of_work_factory,
+) -> None:
+    with unit_of_work_factory() as uow:
+        assert uow.projects is not None
+        project = Project(
+            name="Import Currency Project",
+            operation_type=MiningOperationType.OPEN_PIT,
+        )
+        uow.projects.create(project)
+
+    csv_content = (
+        "project_name,name,currency\n"
+        "Import Currency Project,Invalid Currency,US\n"
+    )
+
+    response = client.post(
+        "/imports/scenarios/preview",
+        files={"file": ("scenarios.csv", csv_content, "text/csv")},
+    )
+
+    assert response.status_code == 200
+    payload = response.json()
+    assert payload["summary"]["accepted"] == 0
+    assert payload["summary"]["errored"] == 1
+    assert payload["parser_errors"]
+    parser_error = payload["parser_errors"][0]
+    assert parser_error["field"] == "currency"
+    assert "Invalid currency code" in parser_error["message"]