Replace Platform-API with updated Postman collection

Add new postman/Nitro Automation Platform APIs.postman_collection.json and remove the old postman/Platform-API.postman_collection.json. The new collection includes organized folders (Authorization, Conversions, Extractions, Transformations, Jobs, Work in Progress), example requests (multipart/form-data and OAuth token), and collection- and folder-level Postman test scripts for response validation. This replaces the previous collection with an updated, renamed export.

Author: brianom