Create a modern, user-friendly Linux tool with a graphical interface (GTK4/libadwaita) that exclusively synchronizes and backs up user profiles. The tool should:
- Automatically detect and backup user data such as ~/.config, ~/.local/share, and ~/.var/app (for Flatpak app data).
- Detect installed Flatpak applications including their configurations, remotes, and overrides (flatpak list, flatpak remotes, flatpak override) and synchronize them.
- Provide an intuitive GUI similar to Pika Backup, with modern design, dark mode, and simple actions ("Backup", "Restore", "Start Sync").
- Offer two modes:
- Backup Mode: Incremental, encrypted backup to local or remote destinations (via BorgBackup in the background).
- Sync Mode: Real-time synchronization between devices (similar to Syncthing, but only for selected profile data).
- User-friendliness: The user simply selects the applications or configurations to synchronize (e.g., Firefox, Thunderbird, VS Code), and the tool handles the rest—including symbolic links and conflict avoidance.
- Automation: Support for scheduled backups and background sync via systemd or cron.
- Goal: A hybrid of Pika Backup (design, security) and Syncthing (real-time sync), specialized for user profiles with Flatpak support.