docs: caveat ssr:false approach and link to fundamentals kit

Recommend the ably-nextjs-fundamentals-kit for production Next.js apps
instead of dynamic(ssr:false), per Steven Lindsay's review feedback.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: maratal

src/pages/docs/push/getting-started/nextjs.mdx

@@ -60,7 +60,7 @@ npm install ably
 
 This step initializes the Ably Realtime client with push notification support and wraps the app in `AblyProvider` so that all child components can access the client via hooks.
 
-Because the Ably SDK runs in the browser, the component must not be server-side rendered. Use Next.js [`dynamic`](https://nextjs.org/docs/app/building-your-application/optimizing/lazy-loading) with `ssr: false` to ensure the Ably client is only ever created in the browser.
+Because the Ably SDK runs in the browser, the component must not be server-side rendered. This guide uses Next.js [`dynamic`](https://nextjs.org/docs/app/building-your-application/optimizing/lazy-loading) with `ssr: false` to keep things simple, but this is not the recommended approach for production apps. For a more complete Next.js integration pattern, see the [ably-nextjs-fundamentals-kit](https://github.com/ably/ably-nextjs-fundamentals-kit).
 
 Create `src/app/push/page.tsx` as the entry point:
 
@@ -78,7 +78,7 @@ export default function PushPage() {
 ```
 </Code>
 
-Then create `src/app/push/PushApp.tsx`. Because this module is only ever loaded client-side (due to `ssr: false`), it is safe to instantiate the Ably client at module scope:
+Then create `src/app/push/PushApp.tsx`. Because this module is only ever loaded client-side (due to `ssr: false`), it is safe to instantiate the Ably client at module scope. In a production app you would instead use `useAbly` from within a component to avoid creating a global client instance:
 
 <Code>
 ```javascript