cupsadmin: CLI, CupsKit, app in progress

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Sources/CUPSAdminApp/CUPSAdminApp.swift

@@ -0,0 +1,12 @@
+import SwiftUI
+
+@main
+struct CUPSAdminApp: App {
+    var body: some Scene {
+        // Single-window utility; SwiftUI saves and restores the window frame.
+        Window("CUPS Admin", id: "main") {
+            ContentView()
+        }
+        .defaultSize(width: 980, height: 640)
+    }
+}