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/Models/ServerConfig.swift

@@ -0,0 +1,38 @@
+import Foundation
+
+struct ServerConfig: Codable, Sendable {
+    var host: String
+    var port: Int?
+    var path: String
+    var token: String
+    var useHttps: Bool
+
+    var baseUrl: String {
+        var url = useHttps ? "https://" : "http://"
+        url += host
+        if let port { url += ":\(port)" }
+        if !path.isEmpty { url += path }
+        return url
+    }
+}
+
+extension ServerConfig {
+    private static let key = "serverConfig"
+    private static let appGroupId = "group.com.magicive.marks"
+
+    static func load() -> ServerConfig? {
+        guard let data = UserDefaults.standard.data(forKey: key) else { return nil }
+        return try? JSONDecoder().decode(ServerConfig.self, from: data)
+    }
+
+    func save() {
+        guard let data = try? JSONEncoder().encode(self) else { return }
+        UserDefaults.standard.set(data, forKey: ServerConfig.key)
+        UserDefaults(suiteName: ServerConfig.appGroupId)?.set(data, forKey: ServerConfig.key)
+    }
+
+    func delete() {
+        UserDefaults.standard.removeObject(forKey: ServerConfig.key)
+        UserDefaults(suiteName: ServerConfig.appGroupId)?.removeObject(forKey: ServerConfig.key)
+    }
+}