feat(fusion_login_audit): settings model + page section

Four x_fc_* fields on res.config.settings backed by ir.config_parameter:
retention_days (default 365, 0 = forever), alert_threshold (5),
alert_window_min (15), alert_enabled (True). New "Login Audit" block
on the General Settings page (gated by base.group_system on the block,
NOT on the inherited view record per CLAUDE.md rule #11).

CLAUDE.md gotchas added during this task:
  #5 Boolean config_parameter fields don't round-trip "False" as a
     string — IrConfigParameter.set_param deletes the row on falsy.
     Test with assertFalse, never assertEqual(..., "False").
  #6 ir.ui.view uses group_ids (Odoo 19 rename mirrored from res.users).
     Setting groups_id on an ir.ui.view record raises ValueError at
     install. (The XML attribute groups="..." on inner nodes is
     unrelated and still works.)

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

fusion_login_audit/models/__init__.py

@@ -1,3 +1,4 @@
 # -*- coding: utf-8 -*-
 from . import fusion_login_audit
 from . import res_users
+from . import res_config_settings