Feature: Expand highlight sync to support Android

[cuspymd]

Summary

Current sync behavior is desktop-centric and has limitations on Android.

Problem

• Cross-device continuity (PC ↔ Android) for highlights is limited.
• Browser-native sync alone has constraints in mobile environments.

Request

• Explore a sync architecture that also covers Android.
• Evaluate alternative sync mechanisms beyond browser sync (e.g., bookmark-based approaches).
• Refer to this add-on as an example of synchronisation on Firefox: GitHub - ReDEnergy/SessionSync: SessionSync

Expected Outcome

• Consistent highlight sync experience across desktop and mobile
• A sync architecture that is less sensitive to platform limitations