docs(toolbar): note that authorized URLs must match the site origin including the port

[singhvishalkr]

Problem

Users who add an entry to "Authorized URLs for Toolbar" that does not match their site's actual origin (specifically, the port) often see the toolbar silently fail to load. This has tripped up at least one user for ~1 hour of debugging (see #9789).

Looking at checkUrlIsAuthorized, matching uses parsedUrl.protocol + '//' + parsedUrl.host, and URL.host includes the port when one is present. So http://localhost and http://localhost:3000 are not a match. The previous docs did not call this out.

Fix

Adds two pieces of guidance to contents/docs/toolbar/index.mdx:

1. A short callout under How to launch the toolbar telling users the authorized URL must match the site origin exactly (including port), with a concrete local-dev example.
2. A troubleshooting entry (#### 3. The authorized URL does not match your site's origin (including port)) that lists the three most common mismatch shapes (missing port, explicit default port like :443, trailing path/query).

No behaviour changes -- docs only.

Closes

Closes #9789.

How I tested

• Read authorizedUrlListLogic.ts to confirm origin matching uses protocol + host (host includes port).
• Rendered the MDX locally to confirm the note and the new #### heading sit in the expected positions within the toolbar page.