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/admin/middleware/protect.js

@@ -3,7 +3,7 @@
  * Utilities to protect admin routes and require admin role
  */
 
-import { getSession } from '../../auth/actions/authActions.js';
+import { getSession } from '@zen/core/features/auth/actions';
 import { redirect } from 'next/navigation';
 
 /**
@@ -17,7 +17,7 @@ import { redirect } from 'next/navigation';
  * 
  * @example
  * // In a server component:
- * import { protectAdmin } from '@zen/core/admin';
+ * import { protectAdmin } from '@zen/core/features/admin';
  * 
  * export default async function AdminPage() {
  *   const session = await protectAdmin();
@@ -47,7 +47,7 @@ async function protectAdmin(options = {}) {
  * @returns {Promise<boolean>} True if user is admin
  * 
  * @example
- * import { isAdmin } from '@zen/core/admin';
+ * import { isAdmin } from '@zen/core/features/admin';
  * 
  * export default async function Page() {
  *   const admin = await isAdmin();