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/config/constants.ts

@@ -0,0 +1,30 @@
+// Storage keys
+export const STORAGE_KEYS = {
+  THEME: 'cabinet-theme',
+  ENABLED_THEMES: 'cabinet-enabled-themes',
+  FAVORITE_SETTINGS: 'admin_favorite_settings',
+  USER_THEME_PREFS: 'user_theme_preferences',
+} as const;
+
+// WebSocket
+export const WS = {
+  MAX_RECONNECT_ATTEMPTS: 5,
+  PING_INTERVAL_MS: 25000,
+  MAX_RECONNECT_DELAY_MS: 30000,
+} as const;
+
+// UI
+export const UI = {
+  RESEND_COOLDOWN_SEC: 60,
+  TELEGRAM_HEADER_ANDROID_PX: 48,
+  TELEGRAM_HEADER_IOS_PX: 45,
+} as const;
+
+// API
+export const API = {
+  TIMEOUT_MS: 30000,
+  BALANCE_STALE_TIME_MS: 30000,
+  TRAFFIC_CACHE_MS: 30000,
+  TRAFFIC_WARN_PERCENT: 70,
+  TRAFFIC_CRITICAL_PERCENT: 90,
+} as const;