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_scenario_validation.py

@@ -278,3 +278,70 @@ class TestScenarioComparisonEndpoint:
         detail = response.json()["detail"]
         assert detail["code"] == "SCENARIO_PROJECT_MISMATCH"
         assert project_a_id != project_b_id
+
+
+class TestScenarioApiCurrencyValidation:
+    def test_create_api_rejects_invalid_currency(
+        self,
+        api_client: TestClient,
+        session_factory: sessionmaker,
+    ) -> None:
+        with UnitOfWork(session_factory=session_factory) as uow:
+            assert uow.projects is not None
+            assert uow.scenarios is not None
+            project = Project(
+                name="Currency Validation Project",
+                operation_type=MiningOperationType.OPEN_PIT,
+            )
+            uow.projects.create(project)
+            project_id = project.id
+
+        response = api_client.post(
+            f"/projects/{project_id}/scenarios",
+            json={
+                "name": "Invalid Currency Scenario",
+                "currency": "US",
+            },
+        )
+
+        assert response.status_code == 422
+        detail = response.json().get("detail", [])
+        assert any(
+            "Invalid currency code" in item.get("msg", "") for item in detail
+        ), detail
+
+        with UnitOfWork(session_factory=session_factory) as uow:
+            assert uow.scenarios is not None
+            scenarios = uow.scenarios.list_for_project(project_id)
+            assert scenarios == []
+
+    def test_create_api_normalises_currency(
+        self,
+        api_client: TestClient,
+        session_factory: sessionmaker,
+    ) -> None:
+        with UnitOfWork(session_factory=session_factory) as uow:
+            assert uow.projects is not None
+            assert uow.scenarios is not None
+            project = Project(
+                name="Currency Normalisation Project",
+                operation_type=MiningOperationType.OPEN_PIT,
+            )
+            uow.projects.create(project)
+            project_id = project.id
+
+        response = api_client.post(
+            f"/projects/{project_id}/scenarios",
+            json={
+                "name": "Normalised Currency Scenario",
+                "currency": "cad",
+            },
+        )
+
+        assert response.status_code == 201
+
+        with UnitOfWork(session_factory=session_factory) as uow:
+            assert uow.scenarios is not None
+            scenarios = uow.scenarios.list_for_project(project_id)
+            assert len(scenarios) == 1
+            assert scenarios[0].currency == "CAD"