refactor: reorganize networking and data bridge scenes

* Move networking scenes under `controllers/networking`
* Move data bridge scene under `scenes/data`
* Rename the bridge node to `data_bridge`
* Update lobby UI scene path
* Remove unused lobby RPC node/script

controllers/networking/game_server.tscn

@@ -0,0 +1,6 @@
+[gd_scene load_steps=2 format=3 uid="uid://bss61m8hfvab3"]
+
+[ext_resource type="Script" uid="uid://bndylf4rwtlkn" path="res://controllers/networking/game_server.gd" id="1_3xapr"]
+
+[node name="server_net" type="Node"]
+script = ExtResource("1_3xapr")