feat(network): export network history as HAR - #459

Summary

Closes #458 - Introduce a native multi-selection HAR 1.2 export feature directly within Network Session History. It allows developers to select network requests and export them into compliant .har files with full payloads (request postData, response content.text, millisecond timing, and accurate startedDateTime), while refactoring the view controller into a clean ViewModel architecture and fixing UIKit cell selection styling.

• HAR 1.2 Full Payload Export: Enables exporting multiple selected session history requests into compliant .har files containing request bodies (postData), response bodies (content.text), millisecond durations, and accurate timestamps parsed from startTime.

Type of change

• Fix
• Feature
• Refactor
• Docs
• CI/CD

Test plan

• Unit tests updated
• Manual testing completed
• CI passing

Manual test steps

1. Navigate to Network -> Session History -> select an existing session.
2. Tap the Share icon.
3. Tap Export (N), share/save the .har file, and open it in Charles, Proxyman, or Chrome DevTools to verify request payload, response body, and individual timestamps are accurately populated.

Screenshots / recordings (if applicable)

Checklist

• I reviewed my own changes
• I updated docs when needed
• I considered backward compatibility