Graceful asndb API failure handling

[liquidsec]

Summary

Closes #3215

• ASN-as-targets (bbot -t ASN:15169): retries 3 times with a 3-second delay between attempts. If all retries fail, the scan aborts cleanly with a message directing the user to look up CIDR ranges manually and pass them directly with -t.
• Mid-scan ASN lookups (asn report module, waf_bypass): circuit breaker on ASNHelper trips after 5 consecutive failures, logs a single prominent warning, and returns UNKNOWN_ASN for all subsequent calls without hitting the network. The scan continues without ASN enrichment data.

[github-actions]

🚀 Performance Benchmark Report

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[codecov]

Codecov Report

❌ Patch coverage is 97.50000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90%. Comparing base (ef65b09) to head (b942be0).

Files with missing lines	Patch %	Lines
bbot/core/helpers/asn.py	88%	2 Missing ⚠️
bbot/core/event/helpers.py	96%	1 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##             dev   #3219    +/-   ##
======================================
+ Coverage     90%     90%    +1%     
======================================
  Files        453     453            
  Lines      46101   46209   +108     
======================================
+ Hits       41211   41328   +117     
+ Misses      4890    4881     -9     

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