chore(deps): update windows-sys to 0.61 and windows-registry to 0.6

[james-crabnebula]

Summary

• Update windows-sys 0.52 → 0.61
• Update windows-registry 0.5 → 0.6
• No API changes required — existing usage (GetNativeSystemInfo, registry reads) is compatible

Verification

• cargo test --workspace --all-targets — pass (macOS, Linux, Windows)
• E2E updater test (build → package → sign → serve → update) — pass (macOS .app, Linux .AppImage, Windows .msi)
• cargo audit — clean
• cargo deny check — advisories ok, bans ok, licenses ok, sources ok
• Compiled and tested on Windows where these crates are actually used

Supersedes #323 and #390

[FabianLars-crabnebula]

just so it's documented, this should raise the msrv, but since we never defined it, that should be fine.