fix: adapt PubkyAuthRequest to bitkit-core v0.1.54 API change

PubkyAuthDetails.kind is now PubkyAuthKind enum instead of String.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ben-kaufman

Bitkit/Models/PubkyAuthRequest.swift

@@ -32,7 +32,7 @@ struct PubkyAuthRequest {
         let serviceNames = permissions.compactMap { extractServiceName($0.path) }
         return PubkyAuthRequest(
             rawUrl: url,
-            kind: details.kind,
+            kind: String(describing: details.kind),
             relay: details.relay,
             permissions: permissions,
             serviceNames: serviceNames