Update recaptcha integration

[burturt]

Recaptcha's "classic" panel is being deprecated and forced to move to google cloud recaptcha, which may or may not break as we are still using version 2 whereas the latest is version 3. Either can update the code to use v3 (10k free requests per month ouch then $8/month! Not sure if our gcloud credit will work towards this) or use something else like hcaptcha

We have until end of 2025, so not a priority for la ctf 2025.