Playground: Redirect corrections (#8087)

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## PR-Codex overview
This PR focuses on updating the routing configuration in the `next.config.mjs` file to allow for dynamic path segments in specific routes.

### Detailed summary
- Changed `source` for `/insight` to `/insight/:path*`, allowing for dynamic paths.
- Changed `source` for `/payments/backend` to `/payments/backend/:path*`, enabling dynamic path handling.
- Both routes maintain their respective `destination` and `permanent` settings.

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<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **Bug Fixes**
  * Fixed redirects for /insight and /payments/backend to handle nested paths, ensuring deep links (e.g., subpages) correctly route to their destinations without 404s.
  * Maintains existing base redirects and leaves other routes untouched, improving navigation reliability without altering overall site behavior.

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Author: MananTank

apps/playground-web/next.config.mjs

@@ -148,12 +148,12 @@ const nextConfig = {
         permanent: false,
       },
       {
-        source: "/insight",
+        source: "/insight/:path*",
         destination: "https://insight.thirdweb.com/reference",
         permanent: false,
       },
       {
-        source: "/payments/backend",
+        source: "/payments/backend/:path*",
         destination: "/reference#tag/payments",
         permanent: false,
       },