feat: add fusion_odoo_fixes module for default Odoo patches

- New standalone module to collect fixes for default Odoo behavior
- Fix #1: account_followup never clears followup_next_action_date
  when invoices are paid, causing collection emails to fully-paid
  clients. Hooks into _invoice_paid_hook to auto-clear stale data.
- Harden Fusion Accounting followup queries with amount_residual > 0
  filter and add balance check before sending emails

Co-authored-by: Cursor <cursoragent@cursor.com>

fusion_odoo_fixes/models/__init__.py

@@ -0,0 +1,5 @@
+# -*- coding: utf-8 -*-
+# Copyright 2025-2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+
+from . import account_move

fusion_odoo_fixes/models/account_move.py

@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+# Copyright 2025-2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+#
+# FIX: account_followup never clears followup_next_action_date
+# ------------------------------------------------------------
+# Odoo's account_followup module sets followup_next_action_date on
+# res.partner when overdue invoices are detected, but never clears it
+# when those invoices are paid.  The daily cron re-evaluates status
+# via SQL so it *usually* skips zero-balance partners, but the stale
+# field causes partners to appear in follow-up lists and manual sends
+# can still fire emails to fully-paid clients.
+#
+# This override hooks into _invoice_paid_hook (called by the core
+# reconciliation engine) and clears the follow-up date when the
+# partner has no remaining receivable balance.
+
+import logging
+
+from odoo import models
+
+_logger = logging.getLogger(__name__)
+
+
+class AccountMove(models.Model):
+    _inherit = 'account.move'
+
+    def _invoice_paid_hook(self):
+        super()._invoice_paid_hook()
+
+        partner_model = self.env['res.partner']
+        if 'followup_next_action_date' not in partner_model._fields:
+            return
+
+        partners = self.mapped('partner_id.commercial_partner_id').filtered(
+            'followup_next_action_date'
+        )
+        if not partners:
+            return
+
+        for partner in partners:
+            has_balance = self.env['account.move.line'].search_count([
+                ('partner_id', '=', partner.id),
+                ('account_id.account_type', '=', 'asset_receivable'),
+                ('parent_state', '=', 'posted'),
+                ('reconciled', '=', False),
+                ('amount_residual', '>', 0),
+            ], limit=1)
+            if not has_balance:
+                partner.write({'followup_next_action_date': False})
+                _logger.info(
+                    "Cleared follow-up for partner %s (ID %s) -- no outstanding balance",
+                    partner.name, partner.id,
+                )