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/modules/posts/api.js

@@ -29,7 +29,7 @@ import {
   validateUpload,
   FILE_TYPE_PRESETS,
   FILE_SIZE_LIMITS
-} from '@hykocx/zen/storage';
+} from '@zen/core/storage';
 
 import { getPostsConfig, getPostType } from './config.js';