refactor: consolidate getCookie into @ui/lib/utils

- Move getCookie function to packages/ui/lib/utils.ts
- Update all imports from @smart-signer/lib/utils to @ui/lib/utils
- Remove getCookie export from smart-signer/lib/utils.ts

Affected files:
- smart-signer/components/auth/process.tsx
- smart-signer/components/login-panel.tsx
- smart-signer/components/signin-panel.tsx
- blog/features/layouts/site-header/client-effects.tsx
- wallet/components/lang-toggle.tsx
- wallet/pages/_app.tsx