Add Comparison Results Export Feature

[pavankalyan-nvs]

Description:
Users need the ability to export comparison results in different formats:

1. Export differences as:
   • HTML report
   • PDF document
   • JSON diff format
   • Plain text summary
2. Include options to customize export format
3. Add ability to save comparison settings

Acceptance Criteria:

• Implement export functionality for all formats
• Add export configuration options
• Create printable view
• Support saving comparison settings
• Add export progress indicator

Priority: Medium