Replace manual backend config with auto JWT auth

Device auto-registers on first launch using hardcoded backend URL
and anon key (MarksAuth.swift). 90-day JWT stored in UserDefaults,
refreshed transparently. No settings fields needed — ClaudeService
is always active and non-optional throughout the app.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Marks/Views/BrowserView.swift

@@ -185,16 +185,15 @@ private struct WebViewRepresentable: UIViewRepresentable {
 struct BrowserView: View {
     let initialURL: URL
     let initialTitle: String
-    let claude: ClaudeService?
+    let claude: ClaudeService
 
     @Environment(\.dismiss) private var dismiss
     @Environment(\.openURL) private var openURL
     @State private var state: BrowserState
     @State private var readerMode = false
     @State private var showPodcast = false
-    @State private var showAISetupAlert = false
 
-    init(url: URL, title: String, claude: ClaudeService? = nil) {
+    init(url: URL, title: String, claude: ClaudeService) {
         self.initialURL = url
         self.initialTitle = title
         self.claude = claude
@@ -262,10 +261,7 @@ struct BrowserView: View {
 
                     Spacer()
 
-                    Button {
-                        if claude != nil { showPodcast = true }
-                        else { showAISetupAlert = true }
-                    } label: {
+                    Button { showPodcast = true } label: {
                         Image(systemName: "headphones")
                     }
                     .disabled(state.isLoading)
@@ -284,14 +280,7 @@ struct BrowserView: View {
             if p > 0.01 { ReadingProgress.set(url: urlStr, progress: p) }
         }
         .sheet(isPresented: $showPodcast) {
-            if let claude {
-                PodcastPlayerView(articleUrl: (state.currentURL ?? initialURL).absoluteString, claude: claude)
-            }
-        }
-        .alert("AI Not Configured", isPresented: $showAISetupAlert) {
-            Button("OK") {}
-        } message: {
-            Text("Add your Backend URL and API Key in Settings to use podcast generation.")
+            PodcastPlayerView(articleUrl: (state.currentURL ?? initialURL).absoluteString, claude: claude)
         }
     }
 }