feat(progression): XP, niveaux et popups flottants (+N XP)

Nouvel autoload PlayerProgress qui gagne de l'XP sur:
- cassage de blocs (gain variable selon le type: perle, épave, coral > sand)
- collecte de perles (+25)
- crafting (+10)
- paliers de profondeur atteints (+20 à 10/25/50/75/100m)

HUD: barre XP + label niveau en bas centre, bannière "NIVEAU X" au level-up
(son bulle + fade). Popup 3D "+N XP" spawn au point d'action.

Boucle court-terme dopamine: chaque action = feedback visuel immédiat.

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

scripts/Main.gd

@@ -225,6 +225,7 @@ func _on_block_break(hit_position: Vector3, _normal: Vector3) -> void:
 		if broken_id > 0:
 			inventory.add_item(broken_id, 1)
 			AudioManager.play_bubble_sfx(hit_position)
+			_award_break_xp(broken_id, hit_position)
 	else:
 		_world_sync.server_break_block(hit_position)
 		AudioManager.play_bubble_sfx(hit_position)
@@ -240,6 +241,24 @@ func _on_block_break(hit_position: Vector3, _normal: Vector3) -> void:
 	burst.emit_burst(hit_position, broken_color)
 
 
+func _award_break_xp(block_id: int, hit_position: Vector3) -> void:
+	var pp: Node = get_node_or_null("/root/PlayerProgress")
+	if pp == null:
+		return
+	var gain: int = pp.XP_BREAK_BY_BLOCK.get(block_id, pp.XP_BREAK_DEFAULT)
+	pp.award(gain, "bloc", hit_position)
+	_spawn_xp_popup(gain, hit_position)
+
+
+func _spawn_xp_popup(amount: int, world_pos: Vector3) -> void:
+	if amount <= 0:
+		return
+	var popup_script: Script = load("res://scripts/progression/XpPopup.gd")
+	if popup_script == null:
+		return
+	popup_script.spawn(self, "+%d XP" % amount, world_pos + Vector3(0, 0.8, 0))
+
+
 func _on_block_place(hit_position: Vector3, normal: Vector3) -> void:
 	var selected: Variant = inventory.get_selected_item()
 	if selected == null: