Add a new JoinMenu.vue component to provide a UI for joining existing games (emits a "join" event and offers Cancel/Join buttons). Improve UX by adding spacing to GameCreationMenu.vue header. Update OnlineMode.vue to import GameCreationMenu. In the API, send a client-side error message when adding a player fails (GameManager.cs now notifies the player's connection with "Spiel Existiert nicht!" before returning null) so users receive immediate feedback when a join attempt is invalid.
jonas
a5019fc27a