Add heir management functionality in Falukant module

- Implemented setHeir method in FalukantService to designate a child as heir, including validation checks for user and child relationships.
- Updated FalukantController to expose the setHeir endpoint, allowing users to set heirs via the API.
- Enhanced FalukantRouter with a new route for setting heirs.
- Modified FamilyView component to include UI elements for setting heirs, with success and error feedback.
- Updated localization files in both German and English to include new translations related to heir management, improving user experience.

backend/controllers/falukantController.js

@@ -92,6 +92,7 @@ class FalukantController {
             if (!result) throw { status: 404, message: 'No family data found' };
             return result;
         });
+        this.setHeir = this._wrapWithUser((userId, req) => this.service.setHeir(userId, req.body.childCharacterId));
         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);