fix(controller): reopen audit log on SIGHUP

[WaylandYang]

Summary

• reopen the audit sink under the writer lock on SIGHUP and emit a log_reopened boundary event
• preserve graceful SIGINT/SIGTERM shutdown, tolerate individual signal-registration failures, and clean up the signal task with the daemon
• replace copytruncate with rename/create plus systemd reload, retaining a safe restart fallback for older installed units
• document the rotation workflow and cover successful and failed reopen paths

Validation

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features -- -D warnings (Linux container)
• cargo test --all (Linux container)
• git diff --check
• verified the Arch logrotate SHA-256 and packaging assertions

Closes #278