feat(gameplay): perles collectibles + recette amulette de soin

Area3D Pearl flottant/tournant qui émet une couleur nacrée, spawned
périodiquement près du joueur (PearlSpawner, 3 max, intervalle 9s,
zone haute du seafloor). Collecte automatique au contact, ajout à
l'inventaire (item 105 Perle). Nouvelle recette : 2 perles + 1 corail
rouge → Amulette de soin (item 106, consommable). Spawner désactivé
sur serveur dédié headless.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/world/Pearl.gd

@@ -0,0 +1,62 @@
+extends Area3D
+
+signal collected(item_id: int)
+
+const ITEM_ID_PEARL: int = 105
+
+var _time: float = 0.0
+var _mesh: MeshInstance3D = null
+var _collected: bool = false
+
+
+func _ready() -> void:
+	monitoring = true
+	monitorable = false
+	body_entered.connect(_on_body_entered)
+	_build_visual()
+	_build_shape()
+
+
+func _build_visual() -> void:
+	_mesh = MeshInstance3D.new()
+	var sphere := SphereMesh.new()
+	sphere.radius = 0.22
+	sphere.height = 0.44
+	sphere.radial_segments = 12
+	sphere.rings = 8
+	_mesh.mesh = sphere
+
+	var mat := StandardMaterial3D.new()
+	mat.albedo_color = Color(0.96, 0.96, 1.0, 1.0)
+	mat.metallic = 0.3
+	mat.roughness = 0.08
+	mat.emission_enabled = true
+	mat.emission = Color(0.85, 0.92, 1.0)
+	mat.emission_energy_multiplier = 0.8
+	_mesh.material_override = mat
+
+	add_child(_mesh)
+
+
+func _build_shape() -> void:
+	var shape := CollisionShape3D.new()
+	var s := SphereShape3D.new()
+	s.radius = 0.75
+	shape.shape = s
+	add_child(shape)
+
+
+func _process(delta: float) -> void:
+	_time += delta
+	if _mesh != null:
+		_mesh.position.y = sin(_time * 2.0) * 0.18
+		_mesh.rotation.y += delta * 1.4
+
+
+func _on_body_entered(body: Node) -> void:
+	if _collected:
+		return
+	if body.is_in_group("player"):
+		_collected = true
+		collected.emit(ITEM_ID_PEARL)
+		queue_free()