Add CSI as a separate column in report export

Add CSI (Customer Satisfaction Index) as a separate field in the report export.

CSI data is already provided to EnderTuring together with telephony data and should be available as an independent column in exported reports.

The purpose is to allow further analysis and correlation between CSI and other EnderTuring metrics, including CSAT Dynamics and Interaction Intensity Dynamics.

Current Behavior

CSI is received from the telephony source but is not available as a separate column in the exported report.

Expected Behavior

Add a dedicated CSI column to the report export.

The exported value should correspond to the CSI value received for the relevant conversation/call.

Acceptance Criteria

1. CSI is available as a separate column in report export.

2. Add a dedicated column to the report export - only if data present

3. The field is included consistently for all records where CSI data is available.

4. If CSI is not available for a conversation, the field remains empty or follows the existing platform behavior for missing values.

5. CSI can be used together with other exported metrics for further external analysis.