fix: localize tray menu and first-launch language

[Decidetto]

Summary

• persist the selected interface language in native settings
• localize every tray-menu entry using the active interface language
• update tray labels immediately when the language changes
• default first launch to the matching supported Windows UI locale, with English fallback
• migrate existing localStorage language choices without changing current users' preferences

Testing

• pnpm check
• pnpm test
• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test
• manually verified live tray-language updates
• manually verified an unsupported nl-NL locale falls back to English on clean first launch

[vercel]

@Decidetto is attempting to deploy a commit to the Aura Team on Vercel.

A member of the Team first needs to authorize it.

[malashkadev]

Thanks for your help!