Group Dependabot updates into weekly/single PRs to cut noise - #1288

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-dotnet@v4, actions/upload-artifact@v4, microsoft/setup-msbuild@v2, roryprimrose/set-vs-sdk-project-version@v1.0.6. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/