fix(deps): remediate remaining security alerts

[Starosdev]

Summary

• update direct frontend dependency families and refresh Yarn and pnpm lockfiles
• pin patched transitive versions for the remaining Dependabot families
• update MailKit to 4.16.0 and SixLabors.ImageSharp to 3.1.11

Validation

• yarn audit --level high
• pnpm audit, no high findings
• yarn build
• yarn lint
• yarn stylelint
• dotnet restore with SDK 8.0.422 for local validation
• dotnet build with analyzers disabled

Known notes: the checked-in global.json still pins SDK 6.0.405, which is not installed locally. The normal SDK 8 analyzer pass reports existing SA1200 findings across the baseline; the compile-only build passes.