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/init.js

@@ -7,7 +7,7 @@
  */
 
 import { CORE_FEATURES } from './features.registry.js';
-import { done, fail, info, step } from '../shared/lib/logger.js';
+import { done, fail, info, step } from '@zen/core/shared/logger';
 
 /**
  * Initialize all core feature databases.