docs(rest-api): add deferred tokenization endpoint

[ecunado]

Summary

• Documents the new GET /transactions/{guid}/token endpoint for deferred tokenization
• Adds DeferredTokenizationResponse object to the REST API objects reference
• Endpoint allows merchants to retrieve a card token from any previously completed card-present transaction (without needing to enable tokenization at transaction time)

Details

The deferred tokenization flow:

1. A card-present is processed normally on the terminal
2. At any point after completion, the merchant calls GET /transactions/{guid}/token with the transaction GUID
3. The response includes a cardToken that can be used for subsequent MOTO operations

Eligible transaction types: sale, refund, preAuthorizationCapture, moToSale and moToRefund.
Non-eligible types (e.g. tip adjustments) return HTTP 400 / error code 3112.

Test plan

• Verify the new endpoint section renders correctly in Docusaurus (yarn start)
• Check the DeferredTokenizationResponse object appears alphabetically in the Objects page between "Device Status" and "Financial Status"
• Verify the internal link from the endpoint to the object (restobjects.md#deferredTokenizationResponse) resolves correctly
• Validate the curl examples match the format used in the rest of the endpoints doc