fix: update stale Trivy vulnerability database

[Britania Rodriguez Reyes (britaniar)]

Summary

• replace the stale mirrored Trivy vulnerability database with the actively maintained official MCR repository
• update all hub, member, and MCS controller image scan steps
• preserve the existing CRITICAL,HIGH and ignore-unfixed: true scan policy

Root cause

The mirrored database was stale and lacked advisories present in mcr.microsoft.com/oss/v2/aquasecurity/trivy-db:2, causing the workflow's existing filters to report zero findings instead of the seven High findings returned by the current database.

Validation

• confirmed exactly three official database repository references
• confirmed zero stale mirror references
• reviewed the workflow diff for unrelated changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 66.95%. Comparing base (556170b) to head (edfaa44).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #399      +/-   ##
==========================================
- Coverage   67.11%   66.95%   -0.16%     
==========================================
  Files          33       33              
  Lines        3783     3783              
==========================================
- Hits         2539     2533       -6     
- Misses       1070     1075       +5     
- Partials      174      175       +1     

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