Refactor route handlers and CMS clients

Refactored the route handlers to use a new `enhanceRouteHandler` function for better control over request handlers and user authentication. CMS clients are now created using factory functions for better encapsulation and control over instance creation. Renamed `client.ts` in 'keystatic' to `keystatic-client.ts`.

packages/cms/keystatic/src/index.ts

@@ -1,2 +1,2 @@
-export * from './client';
+export * from './keystatic-client';
 export * from './content-renderer';

packages/cms/keystatic/src/keystatic-client.ts

@@ -3,7 +3,11 @@ import { Cms, CmsClient } from '@kit/cms';
 import { createKeystaticReader } from './create-reader';
 import { PostEntryProps } from './keystatic.config';
 
-export class KeystaticClient implements CmsClient {
+export function createKeystaticClient() {
+  return new KeystaticClient();
+}
+
+class KeystaticClient implements CmsClient {
   async getContentItems(options: Cms.GetContentItemsOptions) {
     const reader = await createKeystaticReader();