feat(invoicing): managers (+QM+Owner) can create customer invoices

Grant Odoo Billing (account.group_account_invoice) to group_fp_manager via
implied_ids; Quality Manager + Owner inherit it. Billing only (not Accountant);
the SO-origin workflow gate in fusion_plating_jobs is unchanged, so managers
invoice from the Sale Order's Create Invoice action. Tests assert Manager/Owner
get Billing and Shop Manager does not.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

fusion_plating/fusion_plating_invoicing/tests/__init__.py

@@ -0,0 +1,2 @@
+# -*- coding: utf-8 -*-
+from . import test_manager_invoice_permission