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

@@ -19,7 +19,7 @@ struct PubkyAuthPermission {
 
 struct PubkyAuthRequest {
     let rawUrl: String
-    let kind: String
+    let kind: PubkyAuthKind
     let relay: String
     let permissions: [PubkyAuthPermission]
     let serviceNames: [String]