Add member change event handling for real-time updates

This commit introduces a new socket event for member changes, allowing real-time updates when members are created or updated. The backend now emits a 'member:changed' event upon successful member modifications, while the frontend listens for this event to refresh the member list in the DiaryView component. This enhances the interactivity and responsiveness of the application, ensuring users receive immediate feedback on member changes.

backend/services/socketService.js

@@ -104,3 +104,8 @@ export const emitActivityChanged = (clubId, dateId) => {
   emitToClub(clubId, 'activity:changed', { dateId });
 };
 
+// Event für Member-Änderungen (erstellen, aktualisieren)
+export const emitMemberChanged = (clubId) => {
+  emitToClub(clubId, 'member:changed', { clubId });
+};
+