refactor: full codebase cleanup, dependency updates, and lint fixes

Phase 0: Remove ~920 lines of dead code (ThemeBentoPicker, PromoDiscountBadge,
AdminLayout, SettingsSidebar, MovingGradient, EmptyState, miniapp API, unused
types/functions/transitions/skeleton helpers). Fix API barrel file (add 20 missing exports).

Phase 1: Add ErrorBoundary (app/page/widget levels), centralize constants,
add axios timeout, fix staleTime:0 in React Query.

Phase 2: Consolidate hexToHsl, extract email validation, fix duplicate code.

Phase 3: Fix auth race condition (await checkAdminStatus), memoize useCurrency,
add WebSocket message validation.

Phase 4: Extract useBranding, useFeatureFlags, useScrollRestoration from AppShell.

Phase 5: Remove all eslint-disable react-hooks/exhaustive-deps (14 total),
simplify logger, remove deprecated hooks (useBackButton, useTelegramDnd,
useTelegramWebApp).

Dependencies: React 19, react-router 7, zustand 5, i18next 25, react-i18next 16,
eslint-plugin-react-refresh 0.5. Remove unused @lottiefiles/dotlottie-react.
Convert vite manualChunks to function-based approach for react-router v7 compat.

Lint: Fix logger.ts no-unused-expressions, fix react-refresh/only-export-components
in 6 Radix primitive files (const re-exports → direct re-exports), fix
WebSocketProvider exhaustive-deps. Result: 0 errors, 0 warnings.

Add CLAUDE.md to .gitignore.

src/pages/AdminRemnawaveSquadDetail.tsx

@@ -1,11 +1,9 @@
-import { useParams, useNavigate } from 'react-router-dom';
+import { useParams, useNavigate } from 'react-router';
 import { useQuery } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { adminRemnawaveApi, SquadWithLocalInfo } from '../api/adminRemnawave';
 import { AdminBackButton } from '../components/admin';
 import { ServerIcon, UsersIcon, CheckIcon, XIcon } from '../components/icons';
-import { useBackButton } from '../platform/hooks/useBackButton';
-
 // Country flags helper
 const getCountryFlag = (code: string | null | undefined): string => {
   if (!code) return '🌍';
@@ -55,8 +53,6 @@ export default function AdminRemnawaveSquadDetail() {
   const { uuid } = useParams<{ uuid: string }>();
   const navigate = useNavigate();
 
-  useBackButton(() => navigate('/admin/remnawave'));
-
   // Fetch all squads and find the one we need
   const {
     data: squadsData,