feat(fusion_accounting_core): add computed coexistence group + recompute hooks

group_fusion_show_when_enterprise_absent has membership = all internal
users iff no Enterprise accounting module is installed. Membership is
recomputed on module install/uninstall via overrides on ir.module.module.
Used by Phase 1 fusion_bank_rec menus to auto-hide when Enterprise is
active and auto-appear after Enterprise uninstall.

Made-with: Cursor

fusion_accounting_core/models/res_users.py

@@ -0,0 +1,27 @@
+"""Coexistence group membership recomputation."""
+
+from odoo import api, models
+
+
+class ResUsers(models.Model):
+    _inherit = "res.users"
+
+    @api.model
+    def _fusion_recompute_coexistence_group(self):
+        """Set group membership = all internal users iff Enterprise absent.
+
+        Called from ir.module.module.button_immediate_install / uninstall
+        overrides. Idempotent; safe to call multiple times.
+        """
+        group = self.env.ref(
+            'fusion_accounting_core.group_fusion_show_when_enterprise_absent',
+            raise_if_not_found=False,
+        )
+        if not group:
+            return
+        enterprise_installed = self.env['ir.module.module']._fusion_is_enterprise_accounting_installed()
+        if enterprise_installed:
+            group.sudo().write({'user_ids': [(5, 0, 0)]})
+        else:
+            all_internal = self.sudo().search([('share', '=', False)])
+            group.sudo().write({'user_ids': [(6, 0, all_internal.ids)]})