fix: improve WAF detection for 7Cups, Airliners, and Apple Discussions

[Naraka1337]

Summary

Improves core WAF detection logic to resolve false positives on several major sites including 7Cups, Airliners, and Apple Discussions.

Changes

Core Engine (sherlock.py)

• Added detection for AWS WAF / CloudFront Challenges: Added handling for 202 Accepted status codes and x-amzn-waf-action headers.
• Added detection for Varnish Proof-of-Work Challenges: Added fingerprinting for the window.POW_CHALLENGE_DATA challenge page.
• Added detection for Apple Shield Bot Protection: Added fingerprinting for the SecurityVerificationApp class and X-Debug headers.

Testing

• Verified 7Cups and Airliners now correctly return a WAF verdict for non-existing users (previously reported as Claimed).
• Verified Apple Discussions correctly fingerprints the security verification page as WAF.
• Verified the fix for existing users on these sites to ensure accuracy when the tool is challenged.
• Ran project linting via ruff check and all core offline tests via pytest -m "not online". All checks passed.