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/controllers/falukantController.js

@@ -93,6 +93,8 @@ class FalukantController {
             return result;
         });
         this.setHeir = this._wrapWithUser((userId, req) => this.service.setHeir(userId, req.body.childCharacterId));
+        this.getPotentialHeirs = this._wrapWithUser((userId) => this.service.getPotentialHeirs(userId));
+        this.selectHeir = this._wrapWithUser((userId, req) => this.service.selectHeir(userId, req.body.heirId));
         this.acceptMarriageProposal = this._wrapWithUser((userId, req) => this.service.acceptMarriageProposal(userId, req.body.proposalId));
         this.getGifts = this._wrapWithUser((userId) => {
             console.log('🔍 getGifts called with userId:', userId);