Global setting so users can always download from cdn.zapstore.dev instead of
the original URL (e.g. GitHub) to avoid exposing their IP to the host.
- SecureStorageService: getAlwaysUseCdn() / setAlwaysUseCdn() and alwaysUseCdnProvider
- PackageManager: _resolveDownloadUrl() reads the setting and returns CDN or original URL
- InstallAlertDialog: switch "Download from CDN (hides IP)"; relay-signed apps show
dynamic text (CDN vs original URL) based on switch state
- InstallButton: saves alwaysUseCdn from dialog result when user confirms
- ProfileScreen: "Always download from CDN" toggle in Settings
Co-authored-by: Cursor <cursoragent@cursor.com>