chore(deps): ignore SixLabors.ImageSharp major updates (v4 requires paid license)

[JerrettDavis]

Summary

• SixLabors.ImageSharp 4.0.0 requires a paid commercial license (build fails with "No Six Labors license found")
• Adds a Dependabot ignore rule for major-version bumps of SixLabors.ImageSharp under the nuget group so we stay on the OSS-licensed 3.x line
• Unblocks the grouped nuget PR (chore(deps): Bump the nuget-dependencies group with 21 updates #551) so the remaining 20 good updates can be recreated without the offending bump

Test plan

• YAML syntax matches existing file style
• CI checks pass on this PR

[github-actions]

⚠️ Deprecation Warning: The deny-licenses option is deprecated for possible removal in the next major release. For more information, see issue 997.

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[github-actions]

Code Coverage

Summary
  Generated on: 07/03/2026 - 04:09:37
  Coverage date: 07/03/2026 - 04:07:43 - 07/03/2026 - 04:09:29
  Parser: MultiReport (7x Cobertura)
  Assemblies: 23
  Classes: 1067
  Files: 591
  Line coverage: 74.7%
  Covered lines: 36850
  Uncovered lines: 12464
  Coverable lines: 49314
  Total lines: 97285
  Branch coverage: 61.8% (13925 of 22512)
  Covered branches: 13925
  Total branches: 22512
  Method coverage: 86.3% (6312 of 7308)
  Full method coverage: 74.1% (5420 of 7308)
  Covered methods: 6312
  Fully covered methods: 5420
  Total methods: 7308