feat(poc): implement Sprint 1 proof of concept

- project.godot with autoload configuration
- Reception room with placeholder visuals
- Draggable Character with DragDropComponent
- Interactive flower object with bounce animation
- GameState, SaveManager, AudioManager, InputManager autoloads
- HUD with back button and music toggle

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/autoload/AudioManager.gd

@@ -0,0 +1,63 @@
+## AudioManager — music playback with cross-fade, SFX playback, volume control.
+extends Node
+
+const DEFAULT_MUSIC_VOLUME: float = 0.6
+const CROSSFADE_DURATION: float = 1.0
+
+var _music_player_a: AudioStreamPlayer
+var _music_player_b: AudioStreamPlayer
+var _active_player: AudioStreamPlayer
+var _sfx_player: AudioStreamPlayer
+var _music_volume: float = DEFAULT_MUSIC_VOLUME
+var _sfx_volume: float = 1.0
+var _is_fading: bool = false
+
+
+func _ready() -> void:
+	_music_player_a = AudioStreamPlayer.new()
+	_music_player_b = AudioStreamPlayer.new()
+	_sfx_player = AudioStreamPlayer.new()
+	add_child(_music_player_a)
+	add_child(_music_player_b)
+	add_child(_sfx_player)
+	_active_player = _music_player_a
+	_apply_music_volume()
+
+
+func play_music(stream: AudioStream) -> void:
+	if _active_player.stream == stream and _active_player.playing:
+		return
+	var next_player: AudioStreamPlayer = _music_player_b if _active_player == _music_player_a else _music_player_a
+	next_player.stream = stream
+	next_player.volume_db = linear_to_db(0.0)
+	next_player.play()
+	var tween: Tween = create_tween()
+	tween.set_parallel(true)
+	tween.tween_property(_active_player, "volume_db", linear_to_db(0.0), CROSSFADE_DURATION)
+	tween.tween_property(next_player, "volume_db", linear_to_db(_music_volume), CROSSFADE_DURATION)
+	var prev_player: AudioStreamPlayer = _active_player
+	tween.tween_callback(prev_player.stop).set_delay(CROSSFADE_DURATION)
+	_active_player = next_player
+
+
+func play_sfx(stream: AudioStream) -> void:
+	_sfx_player.stream = stream
+	_sfx_player.volume_db = linear_to_db(_sfx_volume)
+	_sfx_player.play()
+
+
+func set_music_volume(value: float) -> void:
+	_music_volume = clampf(value, 0.0, 1.0)
+	_apply_music_volume()
+
+
+func set_sfx_volume(value: float) -> void:
+	_sfx_volume = clampf(value, 0.0, 1.0)
+
+
+func get_music_volume() -> float:
+	return _music_volume
+
+
+func _apply_music_volume() -> void:
+	_active_player.volume_db = linear_to_db(_music_volume)