feat(admin): restructure settings into subpages and hub overview

shop/app/admin/layout.tsx

@@ -77,17 +77,25 @@ export default async function AdminLayout({
               <div className="pt-2 pb-1 px-3">
                 <span className="text-[10px] font-semibold uppercase tracking-wider text-slate-500 dark:text-slate-600">Einstellungen</span>
               </div>
-              <AdminNavLink href="/admin/einstellungen">
-                <Settings className="w-5 h-5" />
-                Allgemein
+              <AdminNavLink href="/admin/einstellungen/firmendaten">
+                <Building2 className="w-5 h-5" />
+                Firmendaten
+              </AdminNavLink>
+              <AdminNavLink href="/admin/einstellungen/branding">
+                <Sparkles className="w-5 h-5 text-violet-400" />
+                Branding & Design
+              </AdminNavLink>
+              <AdminNavLink href="/admin/einstellungen/licserver">
+                <Wrench className="w-5 h-5 text-amber-400" />
+                LicServer
               </AdminNavLink>
               <AdminNavLink href="/admin/settings">
-                <Wrench className="w-5 h-5" />
-                SMTP
+                <Settings className="w-5 h-5 text-sky-400" />
+                SMTP Server
               </AdminNavLink>
-              <AdminNavLink href="/admin/tools">
-                <Database className="w-5 h-5" />
-                DB-Tools
+              <AdminNavLink href="/admin/einstellungen/system">
+                <Database className="w-5 h-5 text-emerald-400" />
+                System & Backup
               </AdminNavLink>
             </>
           )}