Add Windows support

[dviejokfs]

PortZero currently supports macOS and Linux. Windows support is not yet implemented.

What needs to happen

• Replace Unix-specific process management (signals, libc) with cross-platform alternatives
• Handle Windows path separators and localhost resolution differences
• Add Windows CI target to release-cli.yml
• Test Pingora on Windows (may require upstream work)

Platform table

Platform	CLI	Desktop App
macOS (Apple Silicon)	Yes	Yes
macOS (Intel)	Yes	Yes
Linux x86_64	Yes	Yes
Linux aarch64	Yes	--
Windows	Not yet	Not yet

This is a significant effort and could be broken into smaller PRs.