Refactor message bus and lobby networking flow

* Add local message bus emission with optional argument expansion
* Improve message type validation and callback dispatch
* Simplify lobby match join/disconnect handling
* Move lobby server networking toward an overridable `ServerNetworking` base class
* Update lobby scene to use the dedicated lobby server script
* Remove obsolete window configuration and unused RPC stubs

project.godot

@@ -21,10 +21,6 @@ Globals="*res://globals/globals.gd"
 InstanceLauncher="*res://globals/instance_launcher.gd"
 MessageBus="*res://globals/message_bus.gd"
 
-[display]
-
-window/size/always_on_top=true
-
 [rendering]
 
 renderer/rendering_method="gl_compatibility"