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.

frontend/src/i18n/locales/en/falukant.json

@@ -201,6 +201,23 @@
                 "councillor": "Councillor",
                 "assessor": "Assessor"
             }
+        },
+        "family": {
+            "children": {
+                "title": "Children",
+                "name": "Name",
+                "age": "Age",
+                "heir": "Heir",
+                "isHeir": "Heir",
+                "setAsHeir": "Set as Heir",
+                "heirSetSuccess": "The child has been successfully set as heir.",
+                "heirSetError": "Error setting heir.",
+                "actions": "Actions",
+                "none": "No children available.",
+                "detailButton": "Show Details",
+                "addChild": "Add Child",
+                "baptism": "Baptize"
+            }
         }
     }
 }