feat(fusion_login_audit): nightly retention GC cron

Adds _fc_retention_gc() that deletes rows older than the configured
horizon (default 365 days; 0 = keep forever). Registered as a daily
ir.cron. Tests verify both the delete path and the "keep forever"
short-circuit.

Also documents the Odoo 19 gotcha that ir.cron dropped the numbercall
field (the legacy "-1 = run forever" pattern now raises ValueError at
install time; just omit the field).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_login_audit/models/fusion_login_audit.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-from odoo import fields, models
+from odoo import api, fields, models
 
 
 class FusionLoginAudit(models.Model):
@@ -83,3 +83,23 @@ class FusionLoginAudit(models.Model):
     _user_time_idx = models.Index('(user_id, event_time DESC)')
     _login_time_idx = models.Index('(attempted_login, event_time DESC)')
     _geo_state_idx = models.Index('(geo_lookup_state, event_time)')
+
+    @api.model
+    def _fc_retention_gc(self):
+        """Delete audit rows older than `fusion_login_audit.retention_days`.
+        Called daily by ir.cron. retention_days=0 means keep forever."""
+        from datetime import timedelta
+        ICP = self.env['ir.config_parameter'].sudo()
+        try:
+            days = int(ICP.get_param(
+                'fusion_login_audit.retention_days', 365))
+        except (TypeError, ValueError):
+            days = 365
+        if days <= 0:
+            return 0
+        cutoff = fields.Datetime.now() - timedelta(days=days)
+        old = self.sudo().search([('event_time', '<', cutoff)])
+        count = len(old)
+        if old:
+            old.unlink()
+        return count