feat: add Windows native binary support

[rodttu02-vu]

Summary

• Adds browser_windows.go — the missing Windows implementation of openBrowser (using rundll32 url.dll,FileProtocolHandler), matching the pattern of the existing browser_darwin.go and browser_linux.go
• Adds .github/workflows/release-windows.yaml — cross-compiles miactl.exe (windows/amd64) on every push to main and publishes it as a rolling pre-release tagged latest-windows using only GITHUB_TOKEN

Why

miactl has no official Windows binary. Teams running on Windows currently work around this with WSL, which adds friction and a hard dependency on a Linux subsystem. A native binary removes that dependency entirely.

The release workflow intentionally avoids the upstream Goreleaser/Homebrew machinery (which requires BOT_GITHUB_TOKEN) and instead uses a simple rolling pre-release so the latest build is always available via:

gh release download latest-windows --repo <fork> --pattern miactl.exe

Changes

File	Change
internal/authorization/browser_windows.go	New — Windows openBrowser implementation
.github/workflows/release-windows.yaml	New — Windows cross-compile + rolling release workflow

Test plan

• Confirm release-windows workflow runs green on merge
• Confirm latest-windows pre-release appears with miactl.exe asset
• Download binary, run miactl --version to confirm it executes natively on Windows
• Run miactl auth login to exercise the openBrowser path on Windows

[rodttu02-vu]

Hi team — friendly ping on this one. Happy to address any feedback or answer questions. The PR adds a native Windows binary to eliminate the WSL dependency for Windows users. Thanks for your time!

[rodttu02-vu]

Hey team — it's been a week with no feedback on this one. This is a pretty minimal change (66 lines, no modifications to existing code) that unblocks Windows users from needing WSL entirely. Would love even a quick "looks good" or "here's what we'd need changed." Thanks!