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/index.js

@@ -26,7 +26,7 @@ export * as pdf from "./core/pdf/index.js";
 // Export module system as namespace
 export * as moduleSystem from "./core/modules/index.js";
 
-// NOTE: Toast components are CLIENT ONLY - import from '@hykocx/zen/toast'
+// NOTE: Toast components are CLIENT ONLY - import from '@zen/core/toast'
 // Do not export here to avoid mixing client/server boundaries
 
 // Export modules system as namespace (legacy, includes invoice module)