Remove auth tokens from codebase

There are a few checked-in auth tokens in the codebase - specifically, the airbridge token (which is RO) and the recaptcha token (which only applies to Sprig).

While this is bad, and these should be removed from the codebase, the actual potential for harm is very low.

Search the codebase for the airbridge and reCAPTCHA tokens, then inspect how each is used. Remove the checked-in values without breaking the Sprig integration, and verify that no auth tokens remain in tracked files.

Written by the indexing model from the issue text.