feat(fusion_login_audit): smart button + Login Activity tab on res.users

Adds four x_fc_* fields on res.users: login_audit_ids (One2many),
login_audit_count (compute), last_successful_login (compute, stored),
last_login_ip (compute, stored). action_fc_view_login_audit returns
a window action scoped to the current user. View inheritance adds a
smart button to the button box and a "Login Activity" page to the
notebook, both gated by base.group_system on the inner XML nodes
(NOT on the view record — Odoo 19 forbids that; see CLAUDE.md rule #11).

Tests (2 new, 18 total green):
  test_computed_last_successful_login — uses registry cursor to commit
    the audit row so the stored compute picks it up across the
    TransactionCase boundary.
  test_action_view_login_audit_returns_window_action — smart-button
    action shape + domain scoping.

CLAUDE.md rule #11 added: inherited ir.ui.view records cannot have
groups/group_ids on the record; the gate must be on the inner XML nodes.

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',
+        'views/res_users_views.xml',
     ],
     'installable': True,
     'application': False,