feat: add systemd service management

[0x676e67]

Summary

• replace the Unix daemon commands with Linux systemd service management
• install, enable, start, restart, stop, inspect, and follow logs through systemd
• use a persistent platform state directory and systemd StateDirectory for generated certificates
• harden the generated unit and disable ANSI escapes when stderr is not a terminal

Validation

• cargo test (Windows and WSL Ubuntu)
• cargo clippy --all-targets (Windows and WSL Ubuntu)
• cargo +nightly fmt --all -- --check
• WSL systemd runtime and read-only CLI status/help checks