feat(web): sign-in, first-run setup, app shell and user admin (M1)

- core: AuthSession keeps the access token in memory, refreshes it
  once for all parallel requests (single-flight) and retries them;
  refresh races between tabs are retried, reuse signs out; ApiError
  carries problem+json codes and field errors
- web: TanStack Router with guards — guests go to /login, the bootstrap
  admin to /setup/admin, temporary passwords to /setup/password, admin
  pages by role
- login, setup screens, Classic shell (top bar, role-based sidebar,
  empty player), settings: name, theme, language, password, devices
- users admin: search, role filter, create with a one-time temporary
  password, reset, block, role change, delete as the policy allows;
  audit log for admins
- ru/en strings for auth, admin and error codes; language and theme
  are saved in the profile

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/App.tsx

@@ -1,57 +1,30 @@
-import { createApiClient, type ApiClient } from '@pipu/api-client';
-import { checkServer } from '@pipu/core';
-import { SUPPORTED_LOCALES } from '@pipu/i18n';
-import { useQuery } from '@tanstack/react-query';
-import { useTranslation } from 'react-i18next';
+import type { AuthSession } from '@pipu/core';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
+import { RouterProvider } from '@tanstack/react-router';
+import { useState } from 'react';
 
-const defaultClient = createApiClient();
+import type { createAppRouter } from './app/router';
+import { SessionProvider } from './app/session';
 
-export function App({ client = defaultClient }: { client?: ApiClient }) {
-  const { t, i18n } = useTranslation();
-  const server = useQuery({ queryKey: ['server-info'], queryFn: () => checkServer(client) });
+export function createQueryClient() {
+  return new QueryClient({ defaultOptions: { queries: { retry: 1, refetchOnWindowFocus: false } } });
+}
 
+export function App({
+  session,
+  router,
+  queryClient,
+}: {
+  session: AuthSession;
+  router: ReturnType<typeof createAppRouter>;
+  queryClient?: QueryClient;
+}) {
+  const [client] = useState(() => queryClient ?? createQueryClient());
   return (
-    <div className="shell">
-      <header className="top">
-        <div className="logo">
-          <span className="logo-dot" aria-hidden />
-          {t('app.name')}
-        </div>
-        <div className="langs" role="group" aria-label={t('language.label')}>
-          {SUPPORTED_LOCALES.map((l) => (
-            <button
-              key={l}
-              type="button"
-              aria-pressed={i18n.language === l}
-              onClick={() => {
-                void i18n.changeLanguage(l);
-                document.documentElement.lang = l;
-              }}
-            >
-              {l.toUpperCase()}
-            </button>
-          ))}
-        </div>
-      </header>
-      <main className="main">
-        <section className="card">
-          <h1>{t('app.name')}</h1>
-          <p className="muted">{t('app.tagline')}</p>
-          {server.data?.status === 'ok' ? (
-            <div className="status" data-state="ok" role="status">
-              {t('server.online', { version: server.data.info.version })}
-            </div>
-          ) : server.data ? (
-            <div className="status" data-state="error" role="status">
-              {t('server.offline')}
-            </div>
-          ) : (
-            <div className="status" data-state="pending" role="status">
-              {t('server.checking')}
-            </div>
-          )}
-        </section>
-      </main>
-    </div>
+    <SessionProvider session={session}>
+      <QueryClientProvider client={client}>
+        <RouterProvider router={router} />
+      </QueryClientProvider>
+    </SessionProvider>
   );
 }