feat(fusion_login_audit): add _fc_build_event_vals context helper

Single helper builds vals for fusion.login.audit rows from the live
HTTP request, or falls back to ip=''internal'' + geo_lookup_state=''internal''
when there is no request. Parses UA into browser/os/device_type via the
bundled user_agents library. Never reads credential[''password'']. Tests
cover: no-request fallback, UA parsing on a Chrome/Windows UA, and the
regression that no password value leaks into the vals dict.

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

fusion_login_audit/models/__init__.py

@@ -1,2 +1,3 @@
 # -*- coding: utf-8 -*-
 from . import fusion_login_audit
+from . import res_users