deprecate the blacklist3r CLI tool

[liquidsec]

Summary

Removes the standalone blacklist3r.py tool and its tests, and replaces the README section with a deprecation note. The capabilities in the main badsecrets viewstate modules now far surpass what the standalone tool offered, and it had become a maintenance burden.

Changes

• Delete badsecrets/examples/blacklist3r.py
• Delete tests/examples_blacklist3r_test.py
• README: replace the blacklist3r.py subsection with a deprecation notice; the historical "Inspired by Blacklist3r" attribution at the top is preserved

Test plan

• No other code imports blacklist3r (grep clean)
• CI green

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (09956f4) to head (bc9a4bc).
⚠️ Report is 7 commits behind head on dev.

Additional details and impacted files

@@             Coverage Diff             @@
##              dev      #392      +/-   ##
===========================================
+ Coverage   99.85%   100.00%   +0.14%     
===========================================
  Files          31        30       -1     
  Lines        3412      3084     -328     
===========================================
- Hits         3407      3084     -323     
+ Misses          5         0       -5     

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