added first theme progress and switched all files to use static typing

globals/background_music_manager.gd

@@ -0,0 +1,10 @@
+extends Node
+
+@export var music: Array[MusicFile]
+
+func play(_file: String) -> void:
+	pass
+
+# Called when the node enters the scene tree for the first time.
+func _ready() -> void:
+	pass # Replace with function body.