chore: rename package from @hykocx/zen to @zen/core

Update all references across source files, documentation, and
configuration to reflect the new package scope and name. This includes
updating `.npmrc` registry config, install instructions, module
examples, and all import path comments throughout the codebase.

src/features/auth/index.js

@@ -1,8 +1,8 @@
 /**
  * Zen Authentication Module - Server-side utilities
  * 
- * For client components, use '@hykocx/zen/auth/pages'
- * For server actions, use '@hykocx/zen/auth/actions'
+ * For client components, use '@zen/core/auth/pages'
+ * For server actions, use '@zen/core/auth/actions'
  */
 
 // Authentication library (server-side only)