Integrate Frontend with Real-time Validation Endpoint and Fix Calibration Crashes

[suchithgali]

Summary

This pull request connects the frontend process to the newly created backend /api/realtime-validation endpoint. It also adds crucial safeguards to the Vuex store to prevent the frontend from crashing when processing incomplete backend prediction responses.

Changes

• Updates the detectFace loop in DoubleCalibrationRecord.vue to actively stream live user tracking data (x, y coordinates) to the backend's real-time validation endpoint.
• Wrap the API call in a try-catch so network latency or backend validation failures do not interrupt the active UI session.
• Added fallback defaults to the finishCalibration action to map missing prediction metrics to 0.00, preventing TypeError page crashes when backend data is unavailable.

Related Backend PR

ruxailab/eye-tracker-api#101