Prevent overblocking

[etkaar]

Issue #15 unfortunately shows that there is high risk of overblocking, e.g. blocking legitime servers which have nothing to do with the ongoing Valve Master Server exploitation. In that case popular CSS servers with a history of about 15 years were blocked since May 2025.

This can happen due to a mistake, but there is also a high risk from malicious server owners trying to block their competitors without them actually knowing that they got blocked. Not only the server browser can be abused, also this list can be.

We should make sure that proposals from issues are better checked/validated.