ci: fix Windows Actions workflows broken by windows-2019 runner retirement

[x15sr71]

Problem

Both build.yml and release.yml target the windows-2019 GitHub Actions runner, which was fully retired on June 30, 2025. Jobs on this label can no longer be scheduled, which is why builds started failing after PR #14 merged (unrelated to that PR's actual changes).

On top of that, several pinned actions in both workflows are on deprecated majors that either fail outright or emit deprecation warnings on current runners:

• actions/upload-artifact@v1.0.0 — v1–v3 are hard-blocked by GitHub since Jan 30, 2025; any job using them auto-fails.
• actions/checkout@v1 — pinned to the old Node12 action runtime.
• nuget/setup-nuget@v1, microsoft/setup-msbuild@v1.1 — outdated majors.
• softprops/action-gh-release@v1 — v1/v2 are unmaintained; v3 is current.
• thedoctor0/zip-release@master — floating branch ref, not a pinned version (supply-chain risk: whoever pushes to master upstream changes what runs in our release pipeline).

Changes

build.yml

• windows-2019 → windows-2022 (current supported LTS image)
• actions/checkout@v1 → v4
• microsoft/setup-msbuild@v1.1 → v3, and dropped the hardcoded vs-version pin — per upstream's own README, omitting it lets the action auto-detect the installed VS toolset on GitHub-hosted runners, avoiding the exact kind of pin-goes-stale-on-image-update failure we're fixing here.
• nuget/setup-nuget@v1 → v3
• actions/upload-artifact@v1.0.0 → v4

release.yml

• Same runner/checkout/msbuild/nuget fixes as above
• thedoctor0/zip-release@master → pinned to 0.7.6 (latest tagged release)
• softprops/action-gh-release@v1 → v3

Testing

• build.yml triggers on pull_request, so this PR's own CI check is a live smoke test of every change above on the real windows-2022 runner.
• release.yml only triggers on release: created, so it is not exercised by this PR — it'll get its first real test on the next tagged release.