debug: add logging to inventory overlay and backpack for click debugging

inventory/inventory_overlay/InventoryOverlay.gd

@@ -33,6 +33,10 @@ func _ready() -> void:
 	InventoryManager.combination_attempted.connect(_on_combination_attempted)
 
 func show_overlay() -> void:
+	print("[OVERLAY] show_overlay called, inventory has %d items" % InventoryManager.inventory.size())
+
+func hide_overlay() -> void:
+	print("[OVERLAY] hide_overlay called")
 	_refresh_grid()
 	if _fade_tween:
 		_fade_tween.kill()
@@ -95,6 +99,7 @@ func _refresh_grid() -> void:
 	grid.columns = SLOTS_PER_ROW
 
 func _on_slot_clicked(item_id: String) -> void:
+	print("[OVERLAY] _on_slot_clicked: '%s', input_active=%s" % [item_id, input_active])
 	if not input_active:
 		return
 
@@ -179,6 +184,7 @@ func _update_hover_label() -> void:
 		hover_label.text = ""
 
 func _on_background_gui_input(event: InputEvent) -> void:
+	print("[OVERLAY] background clicked")
 	if event is InputEventMouseButton and event.button_index == 1 and event.pressed:
 		hide_overlay()
 		close_requested.emit()