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

fusion_plating/fusion_plating_invoicing/tests/test_manager_invoice_permission.py

@@ -0,0 +1,36 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+"""Manager (+ QM + Owner) imply Odoo Billing so they can invoice.
+
+Spec: docs/superpowers/specs/2026-05-29-manager-invoice-permission-design.md
+"""
+from odoo.tests.common import TransactionCase, tagged
+
+
+@tagged('post_install', '-at_install', 'fp_invoice_perm')
+class TestManagerInvoicePermission(TransactionCase):
+
+    def _user_with(self, group_xmlid):
+        return self.env['res.users'].create({
+            'name': 'PermUser',
+            'login': 'perm_%s' % group_xmlid.split('.')[-1],
+            'group_ids': [(6, 0, [self.env.ref(group_xmlid).id])],
+        })
+
+    def test_manager_has_billing_group(self):
+        manager = self._user_with('fusion_plating.group_fp_manager')
+        self.assertTrue(
+            manager.has_group('account.group_account_invoice'),
+            "Manager should imply Odoo Billing (account.group_account_invoice)",
+        )
+
+    def test_owner_inherits_billing(self):
+        owner = self._user_with('fusion_plating.group_fp_owner')
+        self.assertTrue(owner.has_group('account.group_account_invoice'))
+
+    def test_shop_manager_does_not_get_billing(self):
+        # Shop Manager is BELOW Manager — must NOT inherit Billing
+        # ("managers and ABOVE" scope).
+        shop = self._user_with('fusion_plating.group_fp_shop_manager_v2')
+        self.assertFalse(shop.has_group('account.group_account_invoice'))