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/types/index.ts

@@ -335,25 +335,6 @@ export interface ClassicPurchaseOptions {
 
 export type PurchaseOptions = TariffsPurchaseOptions | ClassicPurchaseOptions;
 
-// Legacy type for backward compatibility
-export interface LegacyPurchaseOptions {
-  currency: string;
-  balance_kopeks: number;
-  balance_label: string;
-  subscription_id: number | null;
-  periods: PeriodOption[];
-  traffic: TrafficConfig;
-  servers: ServersConfig;
-  devices: DevicesConfig;
-  selection: {
-    period_id: string;
-    period_days: number;
-    traffic_value: number;
-    servers: string[];
-    devices: number;
-  };
-}
-
 export interface PurchaseSelection {
   period_id?: string;
   period_days?: number;