[Feature] Export and Import Settings

[esphynox]

Summary

Add a way to export current Keyty settings to a file and import them back later.

This would make it easier to:

• move settings between Macs
• back up a working setup
• restore preferences after reinstalling the app
• support future sharing and debugging workflows

Proposed behavior

• Users can export settings to a structured file.
• Users can import a previously exported settings file.
• Imported settings replace current settings after validation.
• The file format should be versioned from the beginning.

Scope

Initial scope should cover the current persisted settings domains:

• app settings
• shortcut settings
• pointer ring settings
• pointer icon settings
• keyboard visualizer settings

Out of scope

• live file-based config as the primary settings system
• automatic sync between machines
• partial import UI
• cloud storage or integration

Acceptance criteria

• A user can export all supported settings to a file.
• A user can import that file on the same or another machine.
• The file format is versioned.
• Importing older or partially missing payloads is handled safely.
• Tests cover round-trip export/import and validation behavior.