Add urapt-web: web UI for urapt-server instances

A Vite + React 18 + TypeScript SPA, same-origin with the API (no CORS,
no Go server changes). Full management parity with the urapt CLI:

- First-run setup (admin bootstrap via needs_setup), login/logout
- Repositories: list, create, tabbed detail (overview edit/delete,
  members CRUD, distributions/components/architectures manager,
  package list + .deb upload + detail + delete, apt-config panel)
- API tokens: show-once creation + revoke
- Admin users: toggle admin / delete
- Settings + dark mode

Stack: Tailwind + shadcn/ui (New York), React Router v7 (lazy routes),
TanStack Query v5, Zustand, Vitest. Hand-written typed API client
mirroring shared/api + shared/models. Dev proxy forwards /api + /apt
to a local urapt-server; deploy behind nginx/Caddy (see urapt-web/README).

urapt-web/src/features/auth/auth-layout.tsx

@@ -0,0 +1,31 @@
+import type { ReactNode } from "react";
+import { Terminal } from "lucide-react";
+
+interface AuthLayoutProps {
+  title: string;
+  description: string;
+  children: ReactNode;
+  footer?: ReactNode;
+}
+
+export function AuthLayout({ title, description, children, footer }: AuthLayoutProps) {
+  return (
+    <div className="flex min-h-dvh items-center justify-center bg-muted/40 p-4">
+      <div className="w-full max-w-sm space-y-6">
+        <div className="flex flex-col items-center gap-2 text-center">
+          <div className="flex size-10 items-center justify-center rounded-lg bg-primary text-primary-foreground">
+            <Terminal className="size-5" />
+          </div>
+          <div className="space-y-1">
+            <h1 className="text-2xl font-semibold tracking-tight">{title}</h1>
+            <p className="text-sm text-muted-foreground">{description}</p>
+          </div>
+        </div>
+        {children}
+        {footer ? (
+          <div className="text-center text-xs text-muted-foreground">{footer}</div>
+        ) : null}
+      </div>
+    </div>
+  );
+}