fix(app): display study not found message for all modes (#5752)

* fix(app): move study validation to ModeRoute component

- Moved validation from defaultRouteInit.ts to Mode.tsx
- Added dedicated useEffect hook for study validation

* test: add Playwright test for study not found error page across multiple modes

tests/pages/index.ts

@@ -3,6 +3,7 @@ import { MainToolbarPageObject } from './MainToolbarPageObject';
 import { LeftPanelPageObject } from './LeftPanelPageObject';
 import { RightPanelPageObject } from './RightPanelPageObject';
 import { ViewportPageObject } from './ViewportPageObject';
+import { NotFoundStudyPageObject } from './NotFoundStudyPageObject';
 
 export {
   DOMOverlayPageObject,
@@ -10,4 +11,5 @@ export {
   LeftPanelPageObject,
   RightPanelPageObject,
   ViewportPageObject,
+  NotFoundStudyPageObject,
 };