chore: migrate from Trivy to Grype for vulnerability scanning

[JAORMX]

Summary

• Replace aquasecurity/trivy-action with anchore/scan-action (Grype) v7.3.2 for vulnerability scanning
• Remove config scanning job (not supported by Grype)
• Preserve govulncheck job unchanged

Test plan

• Verify Grype scan runs successfully in CI
• Check that SARIF results appear in Security tab

🤖 Generated with Claude Code

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.94%. Comparing base (4d4fbe2) to head (db8ce03).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4288      +/-   ##
==========================================
- Coverage   68.95%   68.94%   -0.02%     
==========================================
  Files         473      473              
  Lines       47854    47854              
==========================================
- Hits        33000    32993       -7     
- Misses      12266    12270       +4     
- Partials     2588     2591       +3     

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