Replace the free-form InvitationError.message(String) case with semantic
cases mapped to L10n keys at the UI boundary (Error.uiText), so user-facing
error text is localized instead of substring-matched from English blobs.
.raw(String) remains only for genuinely dynamic system/core messages.
Localize the CoreNFC alertMessage prompts via existing L10n keys, and add
SwiftLint rules (raw_alert_message, raw_invitation_error) to catch raw
alert strings and literal .raw("…") errors going forward.
Add a native SwiftUI VniDrop app (Send/Receive/Settings) talking to the
Rust core via generated UniFFI Swift bindings, plus the uniffi-bindgen
helper crate. iOS uses a TabView, macOS a NavigationSplitView sidebar.
