Add a POST /security/clamav/start endpoint and SecurityService.start_clamav() to enable+start the ClamAV daemon (tries clamav-daemon and clamd). Add unit tests that mock ServiceControl to verify success/failure and auth. Wire a startClamAV API call into the frontend and extend the Security Overview: richer posture UI, one-click fixes (install, start service, init integrity, update defs), KPIs, icons, and accessibility improvements. Update related styles and file-manager minor styles. This improves operator workflows by allowing a one-click "Start service" posture fix and provides immediate UI feedback when fixes run.