Add heir selection functionality in Falukant module

- Implemented getPotentialHeirs and selectHeir methods in FalukantService to allow users to retrieve and select potential heirs based on specific criteria.
- Updated FalukantController to wrap new methods with user authentication and added corresponding routes in FalukantRouter.
- Enhanced OverviewView component to display heir selection UI when no character is present, including loading states and error handling.
- Added translations for heir selection messages in both German and English locales to improve user experience.

backend/routers/falukantRouter.js

@@ -39,6 +39,8 @@ router.get('/directors', falukantController.getAllDirectors);
 router.post('/directors', falukantController.updateDirector);
 router.post('/family/acceptmarriageproposal', falukantController.acceptMarriageProposal);
 router.post('/family/set-heir', falukantController.setHeir);
+router.get('/heirs/potential', falukantController.getPotentialHeirs);
+router.post('/heirs/select', falukantController.selectHeir);
 router.get('/family/gifts', falukantController.getGifts);
 router.get('/family/children', falukantController.getChildren);
 router.post('/family/gift', falukantController.sendGift);