AppPaths: use Environment.SpecialFolder.ApplicationData for all platforms
- Windows → %APPDATA%\PalladiumWallet (unchanged)
- Linux → ~/.config/PalladiumWallet (XDG standard, was ~/.palladium-wallet)
- macOS → ~/Library/Application Support/PalladiumWallet
AppConfig: change default language from "it" to "en" for new installs.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>