rfc: Revive captcha

[Blaumaus]

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• I have searched Swetrix feature requests and there are no duplicates

Describe the solution you'd like?

1. ..but without these wierd captcha vs web analytics specific projects. just treat captcha events as events
2. ideally replace currect text captcha with a POW one
3. place landing page as /captcha, not captcha.swetrix.com subdomain

Additional context

No response

How important is this feature to you?

1 (Not too important)