fix(frontend): confirm modal, settings display, race guard, and test coverage

- S1: Replace window.confirm() with AppConfirmModal for delete actions
- S4: Add formatHours helper to avoid ugly decimals in settings hints
- W5: Add generation counter to SettingsAdminPanel to prevent stale
  async results when section changes rapidly
- S7: Remove unused ApiRequestError import from useScholarBulkActions
- S2: Add error-path tests for bulk delete/toggle network failures
- S3: Add CSRF boundary tests for bulk-delete and bulk-toggle endpoints

app/api/routers/scholars.py

@@ -53,12 +53,12 @@ def _parse_ids_param(ids: str | None) -> list[int] | None:
         return None
     try:
         return [int(p) for p in parts]
-    except ValueError:
+    except ValueError as exc:
         raise ApiException(
             status_code=400,
             code="invalid_ids_param",
             message="The 'ids' parameter must be a comma-separated list of integers.",
-        )
+        ) from exc
 
 
 @router.get(