Sort the scripts and scenes into folders

main/ holds the main window and top bar, quiz/ the quiz and its parts,
player/ the music player, popups/ every popup and what they share, data/ the
songs, players, playlist and settings, server/ the MusicServer client,
common/ the list row and GameLog, and themes/ the themes and style boxes.

quiz/MusicListPanel.tscn

@@ -0,0 +1,24 @@
+[gd_scene format=3]
+
+[ext_resource type="Script" path="res://quiz/music_list_panel.gd" id="part_script"]
+[ext_resource type="Script" uid="uid://gf1bk6xbe3j" path="res://quiz/scroll_to_end_container.gd" id="7_dj026"]
+[ext_resource type="Theme" uid="uid://rxexo3ur85as" path="res://themes/light_gray_theme.tres" id="7_wxbv6"]
+
+[node name="MusicListPanel" type="PanelContainer" unique_id=2011292375]
+layout_mode = 3
+theme = ExtResource("7_wxbv6")
+offset_right = 1088.0
+offset_bottom = 512.0
+script = ExtResource("part_script")
+
+[node name="ScrollContainer" type="ScrollContainer" parent="." unique_id=707750459]
+layout_mode = 2
+follow_focus = true
+script = ExtResource("7_dj026")
+
+[node name="MusicList" type="VBoxContainer" parent="ScrollContainer" unique_id=373398568]
+unique_name_in_owner = true
+layout_mode = 2
+size_flags_horizontal = 3
+size_flags_vertical = 3
+theme_override_constants/separation = 10