Split Admin module into Status and User Management under one sidemenu dropdown

Splits fn=admin into two independent modules: the original status
dashboard stays at fn=admin, user management moves to a new fn=usr
(IntranetController.AdminUsers.cs, fis.usr.js). Both are now reached
through a single "Administration" sidemenu dropdown (Systemüberwachung /
Benutzerverwaltung) gated by one shared fds_sys > 4 check, per ADR 0015
(supersedes 0014's "fold into one module" choice).

Also fixes the password-reset validation to check only a plain 6-char
minimum instead of silently also requiring ValidatePassword's default
2-uppercase/2-lowercase/2-digit composition, which contradicted the
"mind. 6 Zeichen" message shown to the admin.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Fuchs/js/intranet/fis_texts_gui_de.js

@@ -5,6 +5,8 @@
     , m_todo: 'ToDos'
     , m_bcd: 'BankBuchungen'
     , m_admin: 'Administration'
+    , m_admin_status: 'Systemüberwachung'
+    , m_usr: 'Benutzerverwaltung'
     , rsp: 'Passwort ändern'
     , pnm: 'Die Passwörter stimmen nicht überein'
     , cps: 'Das neue Passwort wurde gespeichert.'