ClientId is a product-level GUID registered at developer.connectwise.com,
not per-MSP. Moved to settings.CW_CLIENT_ID env var. MSPs now only
provide site URL, company ID, public key, and private key.
Also added newline handling note to post_note() — CW Developer Guide
states \n is unsupported in JSON bodies. Needs sandbox testing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>