Score-based captcha misconfiguration and invalid-score handling

## What

score-based captcha (reCAPTCHA) misconfiguration/errors (invalid key type / Error on Invalid Score broken).

## Want

- Score-based captcha (reCAPTCHA) misconfiguration/errors (invalid key type / Error on Invalid Score broken)

## Ideas this came from

- [#17870 reCAPTCHA ERROR for site owner: Invalid key type](https://github.com/goauthentik/authentik/issues/17870) — Hello, I've tried all possible ways to activate reCAPTCHA, but I always get the error message above. Settings from here: https://docs.goauthentik.io/add-secure-
- [#24288 "Error on Invalid Score" for score based captchas appears broken, at least for reCAPTCHA v3](https://github.com/goauthentik/authentik/issues/24288) — I've been having an on-and-off issue with logging into my instance on certain machines/browsers that I finally pinned down as being at the fault of the captcha

Start by reviewing the behavior described in linked issues #17870 and #24288, then locate the score-based captcha configuration and validation entry points. Reproduce the invalid-key-type and invalid-score cases; done means both reCAPTCHA misconfiguration errors and the configured invalid-score behavior work reliably.

Written by the indexing model from the issue text.