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/modules/fis.admin.scss

@@ -188,29 +188,6 @@
         color: #fff;
         border-color: rgba(255, 255, 255, 0.4);
     }
-
-    .adm_users_bd table tbody tr {
-        cursor: pointer;
-
-        &:hover td { background-color: #f3f6fb; }
-    }
-}
-
-.adm_groups_dlg {
-    padding: 0.25rem 0;
-
-    .adm_group_row {
-        display: flex;
-        align-items: center;
-        gap: 0.5rem;
-        padding: 0.35rem 0;
-        border-bottom: 1px solid #eee;
-
-        &:last-child { border-bottom: none; }
-
-        input[type="checkbox"] { margin: 0; }
-        label { margin: 0; font-weight: normal; }
-    }
 }
 
 .adm_note {