Replaced the main window for the PiperApp app in the Piper target with a menu bar.

Piper/Sources/App/PiperApp.swift

@@ -11,6 +11,9 @@ import SwiftData
 
 @main
 struct PiperApp: App {
+    
+    // MARK: Properties
+
     var sharedModelContainer: ModelContainer = {
         let schema = Schema([
             Item.self,
@@ -23,11 +26,15 @@ struct PiperApp: App {
             fatalError("Could not create ModelContainer: \(error)")
         }
     }()
+    
+    // MARK: Body
 
     var body: some Scene {
-        WindowGroup {
+        MenuBarExtra {
-            ContentView()
+            EmptyView()
+        } label: {
+            Image(systemName: "circle.fill")
         }
-        .modelContainer(sharedModelContainer)
     }
+
 }