Split settings into a quiz card and an application Settings popup

- A Quiz settings button under the player bar opens a small card above
  it with the quiz settings, including Auto repeat, which moves there
  from under the player bar. The card does not dim the quiz, so it can
  be changed during a song, and grows to fit its rows.
- A Settings button in the top bar opens the application settings:
  server, fullscreen and songs to download ahead. Quick sync is gone,
  as the server no longer has it, and the server list is in Settings.
- Labels use sentence case, and seconds to hide show as whole numbers.
- Debug builds switch to the local server and a low winning score in
  the Settings autoload, before any scene asks the server for anything.
  The DEBUG label moves to the top bar, so it shows on every tab.
- Search moves from the top bar back to the quiz toolbar, as the
  Statistics tab has its own search.

player/MusicPlayer.tscn

@@ -95,13 +95,3 @@ unique_name_in_owner = true
 custom_minimum_size = Vector2(100, 0)
 layout_mode = 2
 size_flags_vertical = 4
-
-[node name="RepeatSongCheckButton" type="CheckButton" parent="."]
-layout_mode = 0
-offset_top = 40.0
-offset_right = 144.0
-offset_bottom = 71.0
-focus_mode = 0
-button_pressed = true
-action_mode = 0
-text = "Auto repeat"

player/music_player.gd

@@ -1,7 +1,7 @@
 class_name MusicPlayer
 extends Control
-## The bar that plays the songs, with play, restart, progress and volume, and the
-## auto repeat switch under it.
+## The bar that plays the songs, with play, restart, progress and volume. Whether a song
+## repeats is a quiz setting ([code]Settings.auto_repeat_song[/code]).
 
 signal update_song_list
 signal play_next_song
@@ -22,7 +22,6 @@ var song_finished: bool = false
 @onready var progress_slider: HSlider = %MusicPlayerSlider
 @onready var volume_slider: VolumeSlider = %VolumeSlider
 @onready var music_time_label: Label = %MusicTimeLabel
-@onready var auto_repeat_button: CheckButton = $RepeatSongCheckButton
 
 
 func _ready() -> void:
@@ -32,11 +31,6 @@ func _ready() -> void:
 	progress_slider.drag_ended.connect(_on_drag_ended)
 
 	audio_player.finished.connect(_on_finished)
-	auto_repeat_button.pressed.connect(_on_auto_repeat_pressed)
-
-
-func _on_auto_repeat_pressed() -> void:
-	Settings.auto_repeat_song = !Settings.auto_repeat_song
 
 
 func _process(_delta: float) -> void: