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>

packages/i18n/src/index.ts

@@ -1,7 +1,11 @@
 import i18next, { type i18n as I18n } from 'i18next';
 
+import enAdmin from '../locales/en/admin.json';
+import enAuth from '../locales/en/auth.json';
 import enCommon from '../locales/en/common.json';
 import enErrors from '../locales/en/errors.json';
+import ruAdmin from '../locales/ru/admin.json';
+import ruAuth from '../locales/ru/auth.json';
 import ruCommon from '../locales/ru/common.json';
 import ruErrors from '../locales/ru/errors.json';
 
@@ -11,8 +15,8 @@ export type Locale = (typeof SUPPORTED_LOCALES)[number];
 export const DEFAULT_LOCALE: Locale = 'en';
 
 export const resources = {
-  ru: { common: ruCommon, errors: ruErrors },
-  en: { common: enCommon, errors: enErrors },
+  ru: { common: ruCommon, auth: ruAuth, admin: ruAdmin, errors: ruErrors },
+  en: { common: enCommon, auth: enAuth, admin: enAdmin, errors: enErrors },
 } as const;
 
 declare module 'i18next' {
@@ -40,7 +44,7 @@ export async function createI18n(locale: Locale): Promise<I18n> {
     fallbackLng: DEFAULT_LOCALE,
     supportedLngs: [...SUPPORTED_LOCALES],
     defaultNS: 'common',
-    ns: ['common', 'errors'],
+    ns: ['common', 'auth', 'admin', 'errors'],
     resources,
     interpolation: { escapeValue: false },
     returnNull: false,