Implement FCrDNS and other DNS features

[btomaev]

Ref #431
Replaces #682

This pr introduces DNS-based verification features, primarily FCrDNS (#431), to improve client validation.

Implements a VerifyFCrDNS(ip, *pattern) function for strict and pattern-based FCrDNS validation. Adds caching for both forward and reverse DNS lookups to reduce latency and external queries.

Exposes new functions to the policy engine:

• verifyFCrDNS(ip)
• verifyFCrDNS(ip, pattern)
• reverseDNS(ip)
• lookupHost(hostname)
• arpaReverseIP(ip) utility for conversion IP to ARPA reverse notation
• regexSafe(string) utility for safely using dynamic strings in regex patterns.

DNS cache TTL can be configured via the dns_ttl setting in the policy file (default: 300s).

dns_ttl:
  forward: 600
  reverse: 600

Added policies for Telegram, VK, and Yandex bots with verifyFCrDNS for more reliable validation.

Checklist:

• Added a description of the changes to the [Unreleased] section of docs/docs/CHANGELOG.md
• Added test cases to the relevant parts of the codebase
• Ran integration tests npm run test:integration (unsupported on Windows, please use WSL)
• All of my commits have verified signatures

[Xe]

This is excellent. I love it. Well done.

All this is missing is docs for the CEL functions in the expressions docs, but I'll submit a patch with them.

[Xe]

I love this. So much.

[JasonLovesDoggo]

This is the first large PR that i've seen where CI actually passed first try, congrats!! 🥳 🎉🎉

[btomaev]

So, the cache is now stored in the store. I've also slightly refactored DNS methods logic to make it simpler and clearer.
Now, verifyFCrDNS(addr) without specifying a pattern returns true if the IP has no PTR records (but I'm starting to doubt this solution, what do you think?).

[Xe]

- Add Polish locale ([#1292](https://github.com/TecharoHQ/anubis/pull/1309))