refactor: simplify lobby server architecture and update app metadata

* remove legacy data bridge, RPC, and server bootstrap files
* simplify lobby scene and node hierarchy
* rename lobby UI scene path and update signal handlers
* replace the application icon and configure the boot splash
* add project description and version metadata

scenes/screens/lobby_screen/lobby.gd

@@ -1,11 +1,8 @@
 class_name Lobby extends LobbyBase
 
 
-@onready var rpc_signals: Node = $rpc_signals
-
 
 func _ready() -> void:
-	Globals.lobby_data.lobby_ui = self
 	setup_signals()
 
 func _exit_tree() -> void: