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.

routes/exports.py

@@ -121,9 +121,32 @@ async def export_projects(
 ) -> Response:
     project_repo = _ensure_repository(
         getattr(uow, "projects", None), "Project")
+    start = time.perf_counter()
     try:
-        start = time.perf_counter()
         projects = project_repo.filtered_for_export(request.filters)
+    except ValueError as exc:
+        _record_export_audit(
+            uow=uow,
+            dataset="projects",
+            status="failure",
+            export_format=request.format,
+            row_count=0,
+            filename=None,
+        )
+        logger.warning(
+            "export.validation_failed",
+            extra={
+                "event": "export",
+                "dataset": "projects",
+                "status": "validation_failed",
+                "format": request.format.value,
+                "error": str(exc),
+            },
+        )
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
     except Exception as exc:
         _record_export_audit(
             uow=uow,
@@ -145,7 +168,6 @@ async def export_projects(
         raise exc
 
     filename = f"projects-{_timestamp_suffix()}"
-    start = time.perf_counter()
 
     if request.format == ExportFormat.CSV:
         stream = stream_projects_to_csv(projects)
@@ -226,10 +248,33 @@ async def export_scenarios(
 ) -> Response:
     scenario_repo = _ensure_repository(
         getattr(uow, "scenarios", None), "Scenario")
+    start = time.perf_counter()
     try:
-        start = time.perf_counter()
         scenarios = scenario_repo.filtered_for_export(
             request.filters, include_project=True)
+    except ValueError as exc:
+        _record_export_audit(
+            uow=uow,
+            dataset="scenarios",
+            status="failure",
+            export_format=request.format,
+            row_count=0,
+            filename=None,
+        )
+        logger.warning(
+            "export.validation_failed",
+            extra={
+                "event": "export",
+                "dataset": "scenarios",
+                "status": "validation_failed",
+                "format": request.format.value,
+                "error": str(exc),
+            },
+        )
+        raise HTTPException(
+            status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
+            detail=str(exc),
+        ) from exc
     except Exception as exc:
         _record_export_audit(
             uow=uow,
@@ -251,7 +296,6 @@ async def export_scenarios(
         raise exc
 
     filename = f"scenarios-{_timestamp_suffix()}"
-    start = time.perf_counter()
 
     if request.format == ExportFormat.CSV:
         stream = stream_scenarios_to_csv(scenarios)