refactor: reorganize package exports under namespaced paths

- Prefix feature exports with `features/` (auth, admin, provider)
- Prefix shared exports with `shared/` (components, icons, lib, config, logger, rate-limit)
- Add new explicit exports for `shared/logger`, `shared/config`, and `shared/rate-limit`
- Update internal imports to use package self-referencing (`@zen/core/shared/*`) instead of relative paths

src/features/auth/components/index.js

@@ -3,8 +3,8 @@
  *
  * Use these components to build custom auth pages for every flow (login, register, forgot,
  * reset, confirm, logout) so they match your site's style.
- * For a ready-made catch-all auth UI, use AuthPagesClient from '@zen/core/auth/pages'.
- * For the default full-page auth (no custom layout), re-export from '@zen/core/auth/page'.
+ * For a ready-made catch-all auth UI, use AuthPagesClient from '@zen/core/features/auth/pages'.
+ * For the default full-page auth (no custom layout), re-export from '@zen/core/features/auth/page'.
  *
  * --- Custom auth pages (all types) ---
  *
@@ -21,7 +21,7 @@
  *
  * onNavigate receives 'login' | 'register' | 'forgot' | 'reset'. Map to your routes (e.g. /auth/${page}).
  * For reset/confirm, pass email and token from searchParams. Full guide: see README-custom-login.md in this package.
- * Protect routes with protect() from '@zen/core/auth', redirectTo your login path.
+ * Protect routes with protect() from '@zen/core/features/auth', redirectTo your login path.
  *
  * --- Dashboard / user display ---
  *