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/SearchView.swift

@@ -31,14 +31,12 @@ struct SearchView: View {
             .listStyle(.plain)
             .navigationTitle("Search")
             .toolbar {
-                if viewModel.claude != nil {
-                    ToolbarItem(placement: .topBarTrailing) {
-                        Toggle(isOn: $useSemanticSearch) {
-                            Label("Semantic", systemImage: "sparkles")
-                        }
-                        .toggleStyle(.button)
-                        .onChange(of: useSemanticSearch) { _, _ in scheduleSearch() }
+                ToolbarItem(placement: .topBarTrailing) {
+                    Toggle(isOn: $useSemanticSearch) {
+                        Label("Semantic", systemImage: "sparkles")
                     }
+                    .toggleStyle(.button)
+                    .onChange(of: useSemanticSearch) { _, _ in scheduleSearch() }
                 }
             }
             .overlay {
@@ -72,7 +70,8 @@ struct SearchView: View {
     private func scheduleSearch() {
         semanticResults = nil
         searchTask?.cancel()
-        guard !searchText.isEmpty, useSemanticSearch, let claude = viewModel.claude else { return }
+        guard !searchText.isEmpty, useSemanticSearch else { return }
+        let claude = viewModel.claude
         searchTask = Task {
             try? await Task.sleep(for: .milliseconds(500))
             guard !Task.isCancelled else { return }