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/hooks/useBranding.ts

@@ -0,0 +1,79 @@
+import { useEffect } from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { useAuthStore } from '@/store/auth';
+import { useTelegramSDK, setCachedFullscreenEnabled } from '@/hooks/useTelegramSDK';
+import {
+  brandingApi,
+  getCachedBranding,
+  setCachedBranding,
+  preloadLogo,
+  isLogoPreloaded,
+} from '@/api/branding';
+
+const FALLBACK_NAME = import.meta.env.VITE_APP_NAME || 'Cabinet';
+const FALLBACK_LOGO = import.meta.env.VITE_APP_LOGO || 'V';
+
+export function useBranding() {
+  const { isAuthenticated } = useAuthStore();
+  const { isFullscreen, isTelegramWebApp, requestFullscreen, isMobile } = useTelegramSDK();
+
+  // Branding data
+  const { data: branding } = useQuery({
+    queryKey: ['branding'],
+    queryFn: async () => {
+      const data = await brandingApi.getBranding();
+      setCachedBranding(data);
+      preloadLogo(data);
+      return data;
+    },
+    initialData: getCachedBranding() ?? undefined,
+    staleTime: 60000,
+    enabled: isAuthenticated,
+  });
+
+  const appName = branding ? branding.name : FALLBACK_NAME;
+  const logoLetter = branding?.logo_letter || FALLBACK_LOGO;
+  const hasCustomLogo = branding?.has_custom_logo || false;
+  const logoUrl = branding ? brandingApi.getLogoUrl(branding) : null;
+
+  // Set document title
+  useEffect(() => {
+    document.title = appName || 'VPN';
+  }, [appName]);
+
+  // Update favicon
+  useEffect(() => {
+    if (!logoUrl) return;
+
+    const link =
+      document.querySelector<HTMLLinkElement>("link[rel*='icon']") ||
+      document.createElement('link');
+    link.type = 'image/x-icon';
+    link.rel = 'shortcut icon';
+    link.href = logoUrl;
+    document.head.appendChild(link);
+  }, [logoUrl]);
+
+  // Fullscreen setting from server
+  const { data: fullscreenSetting } = useQuery({
+    queryKey: ['fullscreen-enabled'],
+    queryFn: brandingApi.getFullscreenEnabled,
+    staleTime: 60000,
+  });
+
+  useEffect(() => {
+    if (!fullscreenSetting || !isTelegramWebApp) return;
+    setCachedFullscreenEnabled(fullscreenSetting.enabled);
+    if (fullscreenSetting.enabled && !isFullscreen && isMobile) {
+      requestFullscreen();
+    }
+  }, [fullscreenSetting, isTelegramWebApp, isFullscreen, requestFullscreen, isMobile]);
+
+  return {
+    appName,
+    logoLetter,
+    hasCustomLogo,
+    logoUrl,
+    isLogoPreloaded,
+  };
+}