feat: export / report generation for various tabs

[NotYuSheng]

Summary

Add export / report generation functionality across the major analysis tabs so users can share or archive findings outside the application.

Motivation

Analysts often need to share findings with colleagues or include them in incident reports. Currently export is limited to CSV in the Conversations tab. A more comprehensive, cross-tab export (ideally as a structured report) would significantly improve usability.

Proposed behaviour

Tab	Suggested export formats
Conversations	CSV (exists), PDF report
Timeline	CSV, PDF
Network Topology	PNG/SVG image, JSON
Packets / Deep inspection	CSV, JSON
Custom Signatures matched	CSV, PDF

• A single "Export / Report" button or dropdown per tab that offers the relevant formats.
• PDF reports should include the tab title, applied filters, timestamp, and a summary table.
• Exported filenames should include the PCAP name and current date/time.

Acceptance criteria

• At least PDF and CSV export available for Conversations and Timeline tabs.
• Exported files include applied filter state.
• Filename includes PCAP identifier and export timestamp.