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/Docs/Decisions/0014-admin-user-management.md

@@ -1,5 +1,5 @@
 ---
-status: Accepted
+status: Superseded
 date: 2026-09-09
 applyTo:
   - "Fuchs/Controllers/IntranetController.Admin.cs"
@@ -7,7 +7,7 @@ applyTo:
   - "Fuchs/js/intranet/modules/fis.admin.scss"
   - "Fuchs_Database/dbo/Functions/fis_admin_*.sql"
   - "Fuchs_Database/dbo/Stored Procedures/fis_admin_*.sql"
-supersededBy: ""
+supersededBy: "0015-split-admin-user-management-module.md"
 ---
 
 # 0014 — Admin user management: folded into the `admin` module, dual auth axis, password always emailed