feat: Windows Service wrapper for production deployments

[stylebending]

Summary

Adds Windows Service support allowing the engine to run as a background Windows service for production deployments.

Changes

• Add windows-service crate dependency for Windows SCM integration
• Implement service install/uninstall via --install / --uninstall flags
• Add proper service control handling (stop command support)
• Report service status to Windows Service Control Manager (Running → Stopping → Stopped)
• Graceful shutdown that stops all plugins before exit
• Service logging to %PROGRAMDATA%\win_event_engine\logs\service.log
• Service config location: %PROGRAMDATA%\win_event_engine\config\config.toml

Usage

# Install as Windows Service (requires admin)
engine.exe --install
# Start the service
sc start WinEventEngine
# Stop the service
sc stop WinEventEngine
# Uninstall
engine.exe --uninstall

Testing

• Service installs successfully
• Service starts and runs
• Service stops gracefully
• Logs written to service.log