Settings file or import/export for settings and filters #3654

📝 Provide a description of the new feature

I'd like a way to keep my Gitify settings and filters in a file, so I can version them in my dotfiles repo and share them across machines.

Right now everything lives in the app's local storage (gitify-settings, gitify-filters, gitify-accounts) inside the LevelDB files under ~/Library/Application Support/gitify/Local Storage/leveldb/. That's binary, the app writes to it while running, and it also holds account tokens, so I can't copy it between machines or manage it with a dotfiles tool like chezmoi.

My use case: I use different filters on my work and personal machines. With a plain JSON file I could template the work vs personal differences and keep the shared parts in one place.

Either of these would work for me:

1. Gitify reads settings and filters from a JSON file at startup (for example in the user data directory), and writes changes back to it.
2. Import/export of settings and filters to a JSON file from the Settings screen.

Either way, account tokens should stay out of the file.

Relevant Forge(s)

All / Not applicable

➕ Additional Information

Tested on Gitify 8.0.0 on macOS. I searched existing issues for export, import, config file, sync, and backup and didn't find a duplicate.