Replace Flutter app with native SwiftUI rewrite (iOS 26)

Complete ground-up rewrite in SwiftUI targeting iOS 26. Drops the Flutter/Dart
codebase entirely in favour of a lean native app with no third-party dependencies.

Features shipped:
- Bookmark list with pagination, pull-to-refresh, swipe delete/archive
- Add bookmark form + iOS share extension (zero-tap save from any app)
- Tags tab — all tags sorted by count, tap to browse filtered bookmarks
- Native search tab (Tab role: .search) with instant client-side filtering
- AI enrichment via OpenRouter (google/gemini-2.0-flash-lite-001): auto-summary
  and tag generation, semantic search, smart collections
- Settings: linkding server config, OpenRouter API key
- App Groups for credential sharing between main app and share extension
- Swift 6 strict concurrency throughout (@Observable, @MainActor)

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

Marks/Views/SettingsView.swift

@@ -0,0 +1,58 @@
+import SwiftUI
+
+struct SettingsView: View {
+    @Bindable var viewModel: BookmarksViewModel
+    let onDisconnect: () -> Void
+
+    @State private var claudeKey = UserDefaults.standard.string(forKey: ClaudeService.defaultsKey) ?? ""
+    @Environment(\.dismiss) private var dismiss
+
+    var body: some View {
+        NavigationStack {
+            List {
+                Section("AI Features") {
+                    VStack(alignment: .leading, spacing: 6) {
+                        Text("OpenRouter API Key")
+                            .font(.system(size: 13, weight: .medium))
+                            .foregroundStyle(.secondary)
+                        SecureField("sk-or-…", text: $claudeKey)
+                            .textContentType(.password)
+                            .autocorrectionDisabled()
+                            .textInputAutocapitalization(.never)
+                            .onChange(of: claudeKey) { _, new in
+                                ClaudeService.save(apiKey: new)
+                                viewModel.updateClaude(new.isEmpty ? nil : ClaudeService(apiKey: new))
+                            }
+                    }
+                    .padding(.vertical, 4)
+
+                    if viewModel.claude != nil {
+                        Label("AI enabled — semantic search, auto-tagging, and smart collections active.", systemImage: "sparkles")
+                            .font(.system(size: 13))
+                            .foregroundStyle(.secondary)
+                    } else {
+                        Text("Add an OpenRouter API key to enable AI features. Uses Gemini 2.0 Flash Lite — very cheap.")
+                            .font(.system(size: 13))
+                            .foregroundStyle(.secondary)
+                    }
+                }
+
+                Section("Server") {
+                    Button(role: .destructive) {
+                        dismiss()
+                        onDisconnect()
+                    } label: {
+                        Label("Disconnect", systemImage: "person.crop.circle.badge.minus")
+                    }
+                }
+            }
+            .navigationTitle("Settings")
+            .navigationBarTitleDisplayMode(.inline)
+            .toolbar {
+                ToolbarItem(placement: .topBarTrailing) {
+                    Button("Done") { dismiss() }
+                }
+            }
+        }
+    }
+}