test(better auth): implementation start of better auth

frontend/src/routes/_adminLayout/-components/Nav.tsx

@@ -0,0 +1,23 @@
+import { Link } from "@tanstack/react-router";
+
+export default function Nav() {
+    return (
+        <div>
+            <nav className="flex gap-1">
+                <Link
+                    to="/admin"
+                    className="[&.active]:font-bold"
+                    activeOptions={{ exact: true }}
+                >
+                    Admin
+                </Link>
+                <Link to="/admin/servers" className="[&.active]:font-bold">
+                    Servers
+                </Link>
+                <Link to="/admin/users" className="[&.active]:font-bold">
+                    Users
+                </Link>
+            </nav>
+        </div>
+    );
+}

frontend/src/routes/_adminLayout/-components/Server.tsx

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+import { getRouteApi } from "@tanstack/react-router";
+
+export default function Server() {
+    const { useParams } = getRouteApi("/_adminLayout/admin/servers/$serverId");
+
+    const { serverId } = useParams();
+    return <div>server id {serverId}!</div>;
+}