feat: add native macOS menu-bar application shell (#1)

TraccarClient/Application/TraccarClientApp.swift

@@ -0,0 +1,29 @@
+import AppKit
+import SwiftUI
+
+@main
+struct TraccarClientApp: App {
+    @NSApplicationDelegateAdaptor(ApplicationDelegate.self) private var delegate
+
+    var body: some Scene {
+        MenuBarExtra {
+            TrackingMenu()
+        } label: {
+            Image("MenuBarIcon")
+                .renderingMode(.template)
+                .accessibilityLabel("Traccar Client — Paused")
+        }
+        .menuBarExtraStyle(.menu)
+
+        Settings {
+            SettingsView()
+        }
+    }
+}
+
+@MainActor
+final class ApplicationDelegate: NSObject, NSApplicationDelegate {
+    func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
+        false
+    }
+}