feat: animated GIF covers with config toggle and focus-based pausing

- Add settings menu with 'Animate GIF covers' toggle (default: off)
- When enabled: extract all GIF frames via ffmpeg, build AnimatedTexture
- When disabled: extract first frame only (static ImageTexture)
- AnimatedTexture starts paused — unpauses only when card has focus
- Focus-based pausing via gui_focus_changed signal (walks up to GameCard)
- Parse GIF89a frame delays for accurate animation speed
- Cache invalidation when setting changes (no restart needed)
- Cache AnimatedTextures in memory to avoid re-extraction
- Bump to v0.1.13

core/artprovider_settings.gd

@@ -0,0 +1,25 @@
+extends VBoxContainer
+
+## Settings screen for the itch.io art provider.
+##
+## Provides a toggle for animated GIF covers. When enabled, GIF cover art
+## is extracted frame-by-frame and displayed as an AnimatedTexture that
+## pauses when the card loses focus.
+
+var settings_manager := load("res://core/global/settings_manager.tres") as SettingsManager
+
+const SETTING_SECTION := "plugin.artprovider"
+const SETTING_ANIMATED_GIFS := "animated_gifs"
+
+@onready var animated_toggle: Toggle = $%AnimatedGifsToggle
+
+
+func _ready() -> void:
+	animated_toggle.button_pressed = settings_manager.get_value(
+		SETTING_SECTION, SETTING_ANIMATED_GIFS, false
+	) as bool
+	animated_toggle.toggled.connect(_on_animated_gifs_toggled)
+
+
+func _on_animated_gifs_toggled(pressed: bool) -> void:
+	settings_manager.set_value(SETTING_SECTION, SETTING_ANIMATED_GIFS, pressed)