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/AdminPaymentMethodEdit.tsx

@@ -1,10 +1,9 @@
 import { useState, useEffect } from 'react';
-import { useParams, useNavigate } from 'react-router-dom';
+import { useParams, useNavigate } from 'react-router';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useTranslation } from 'react-i18next';
 import { adminPaymentMethodsApi } from '../api/adminPaymentMethods';
 import type { PromoGroupSimple } from '../types';
-import { useBackButton } from '../platform/hooks/useBackButton';
 import { usePlatform } from '../platform/hooks/usePlatform';
 
 const BackIcon = () => (
@@ -72,9 +71,6 @@ export default function AdminPaymentMethodEdit() {
   const queryClient = useQueryClient();
   const { capabilities } = usePlatform();
 
-  // Use native Telegram back button in Mini App
-  useBackButton(() => navigate('/admin/payment-methods'));
-
   // Fetch payment methods
   const { data: methods, isLoading } = useQuery({
     queryKey: ['admin-payment-methods'],