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/shared/lib/init.js

@@ -14,7 +14,7 @@
  * }
  */
 
-import { configureRouter, registerFeatureRoutes, clearRouterConfig, clearFeatureRoutes } from '../../core/api/index.js';
+import { configureRouter, registerFeatureRoutes, clearRouterConfig, clearFeatureRoutes } from '@zen/core/api';
 import { validateSession } from '../../features/auth/lib/session.js';
 import { routes as authRoutes } from '../../features/auth/api.js';
 import { done, warn } from './logger.js';