refactor(apple): make InvitationError typed and localize NFC prompts

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.

apple/VniDrop/Core/FileSystemService.swift

@@ -52,7 +52,7 @@ extension FileSystemService {
 	func canRevealReceiveFolder(_ folder: ReceiveFolder) -> Bool { false }
 
 	func revealReceiveFolder(_ folder: ReceiveFolder) async -> Result<Void, Error> {
-		.failure(InvitationError.message("Revealing the receive folder is not supported"))
+		.failure(InvitationError.unsupportedOperation)
 	}
 
 	func discardPickedFiles(_ files: [PickedShareFile]) async {}