chore: add snyk security scan skill

[mwbrooks]

Changelog

• N/A

Summary

This pull request adds a /snyk Claude Code skill for running monthly Snyk security scans.

The skill runs snyk test (dependencies) and snyk code test (source code), summarizes findings by severity, and presents a prioritized action plan.

Preview

• N/A

Testing

• Invoke /snyk in Claude Code and verify both snyk test and snyk code test execute and produce a summary

Requirements

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.24%. Comparing base (783ac1a) to head (d1940c7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #518      +/-   ##
==========================================
- Coverage   71.25%   71.24%   -0.01%     
==========================================
  Files         222      222              
  Lines       18682    18682              
==========================================
- Hits        13311    13310       -1     
+ Misses       4190     4189       -1     
- Partials     1181     1183       +2     

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