feat(fusion_login_audit): failure-burst alert email + cooldown

Mail template + helpers (_fc_alert_*, _fc_recent_failure_count,
_fc_send_failure_alert) wired into _check_credentials so that crossing
the consecutive-failure threshold within the window queues exactly one
mail.mail per attempted login per 60-minute cooldown. Master switch
x_fc_login_audit_alert_enabled honoured. Recipients are members of
base.group_system with a non-empty email and share=False; the
__system__ superuser is excluded by Odoo''s default user filter.

Tests (3 new, 22 total green):
  test_failure_burst_queues_one_email
  test_cooldown_suppresses_second_alert
  test_alert_disabled_master_switch

setUp ensures base.user_admin has an email (fusion-dev''s admin user
ships without one; the only user with an email is __system__, which
is filtered out of standard res.users searches).

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

fusion_login_audit/__manifest__.py

@@ -26,6 +26,7 @@ bursts. Daily retention cron honours a configurable horizon.
     'data': [
         'security/ir.model.access.csv',
         'security/security.xml',
+        'data/mail_template_data.xml',
         'views/fusion_login_audit_views.xml',
         'views/res_users_views.xml',
         'views/res_config_settings_views.xml',