feat(game): add free ball mode and improve ball state handling

* add Free Ball game mode and lobby selection
* refactor base mode ball state tracking for reaped/sunk balls
* add player ownership tracking and colored-ball support
* add initial 9-ball mode implementation
* update 8-ball and snooker modes to use base ball handling
* replicate ball linear velocity for multiplayer synchronization
* improve ball collision sound propagation and physics settings
* reenable game music and initialize game signals
* improve lobby input focus and mode selection behavior
* adjust cue impulse origin and default game mode

controllers/game/modes/free_ball.gd

@@ -0,0 +1,25 @@
+class_name FreeBall extends BaseMode
+
+
+func reap_ball(ball: Node3D) -> void:
+	super(ball)
+
+func process_ball(ball: Node3D) -> void:
+	super(ball)
+
+func handle_switch_user() -> void:
+	push_warning("Balls reaped: ", balls_reaped.size() )
+	push_warning("Balls sunk: ",   balls_sunk.size()   )
+
+	if not balls_reaped.is_empty():
+		# TODO: Handle points, etc
+		balls_reaped.clear()
+
+	if balls_sunk.is_empty():
+		Globals.game_state.switch_active_player()
+		return
+
+	# TODO: Handle points, etc
+	# Globals.multiplayer_data.current_turn_player_id
+
+	balls_sunk.clear()