chore: update project references and add Citron copyright

- Replaced all references to the old project name with Citron.
- Added Citron copyright information alongside existing notices in all files.

src/citron/multiplayer/lobby.h

@@ -11,7 +11,7 @@
 #include "common/announce_multiplayer_room.h"
 #include "network/announce_multiplayer_session.h"
 #include "network/network.h"
-#include "yuzu/multiplayer/validation.h"
+#include "citron/multiplayer/validation.h"
 
 namespace Ui {
 class Lobby;