feat(apple): Add button to show menuBar from FirstTimeView (#5505)

Fixes #5500 

Unfortunately showing the menubar menu _only_ on re-launch is
non-trivial due to the way "re-launches" are processed in macOS.

We can handle them with the `applicationDidBecomeActive` override in
`AppDelegate`, but then this will be triggered whenever we sign in, open
Settings, or open About window because we activate the app then as well
in order to bring the Window to the foreground.

There's no good to way to determine who asked us to activate either.

Instead, we show the Welcome window (FirstTimeView on macOS), and in
there is a new button to show the app menu to use as a fallback for
users who need an alternative way to open the menu with a busy menubar.


<img width="1012" alt="Screenshot 2024-06-23 at 5 14 57 PM"
src="https://github.com/firezone/firezone/assets/167144/1a7dde08-1e83-4dc8-9516-e0390f29c941">

swift/apple/Firezone/Application/FirezoneApp.swift

@@ -36,7 +36,10 @@ struct FirezoneApp: App {
       "Welcome to Firezone",
       id: AppViewModel.WindowDefinition.main.identifier
     ) {
-      AppView(model: appViewModel)
+      if let menuBar = appDelegate.menuBar {
+        // menuBar will be initialized by this point
+        AppView(model: appViewModel).environmentObject(menuBar)
+      }
     }
     .handlesExternalEvents(
       matching: [AppViewModel.WindowDefinition.main.externalEventMatchString]
@@ -58,7 +61,7 @@ struct FirezoneApp: App {
 #if os(macOS)
   @MainActor
   final class AppDelegate: NSObject, NSApplicationDelegate {
-    private var menuBar: MenuBar?
+    var menuBar: MenuBar?
     public var store: Store?
 
     func applicationDidFinishLaunching(_: Notification) {

swift/apple/FirezoneKit/Sources/FirezoneKit/Views/FirstTimeView.swift

@@ -9,6 +9,8 @@ import SwiftUI
 
 #if os(macOS)
 struct FirstTimeView: View {
+  @EnvironmentObject var menuBar: MenuBar
+
   var body: some View {
     VStack(
       alignment: .center,
@@ -21,17 +23,27 @@ struct FirstTimeView: View {
           .padding(.horizontal, 10)
         Spacer()
         Text(
-          "You can sign in to Firezone by clicking on the Firezone icon in the macOS menu bar.\nYou may now close this window."
+          "You can sign in by clicking the Firezone icon in the macOS menu bar or clicking 'Open menu' below."
         )
         .font(.body)
         .multilineTextAlignment(.center)
 
         Spacer()
-        Button("Close this Window") {
-          AppViewModel.WindowDefinition.main.window()?.close()
+        HStack {
+          Button("Close this window") {
+            AppViewModel.WindowDefinition.main.window()?.close()
+          }
+          .buttonStyle(.borderedProminent)
+          .controlSize(.large)
+          Button("Open menu") {
+            DispatchQueue.main.async {
+              menuBar.showMenu()
+            }
+            AppViewModel.WindowDefinition.main.window()?.close()
+          }
+          .buttonStyle(.borderedProminent)
+          .controlSize(.large)
         }
-        .buttonStyle(.borderedProminent)
-        .controlSize(.large)
         Spacer()
           .frame(maxHeight: 20)
         Text(

swift/apple/FirezoneKit/Sources/FirezoneKit/Views/MenuBar.swift

@@ -16,7 +16,7 @@ import SwiftUI
 @MainActor
 // TODO: Refactor to MenuBarExtra for macOS 13+
 // https://developer.apple.com/documentation/swiftui/menubarextra
-public final class MenuBar: NSObject {
+public final class MenuBar: NSObject, ObservableObject {
   private var statusItem: NSStatusItem
   private var resources: [Resource]?
   private var cancellables: Set<AnyCancellable> = []
@@ -48,6 +48,10 @@ public final class MenuBar: NSObject {
     setupObservers()
   }
 
+  func showMenu() {
+    statusItem.button?.performClick(nil)
+  }
+
   private func setupObservers() {
     model.store.$status
       .receive(on: DispatchQueue.main)