fix(app): show the actual running app icon in About, not a named lookup

NSImage(named: "AppIcon") doesn't reliably resolve an App Icon
asset-catalog entry on macOS (it stayed nil / fell back to the SF
Symbol placeholder even with a valid icon in the catalog).
NSApp.applicationIconImage is guaranteed to match whatever the Dock
and Finder are actually showing for the running app.

Outpost/Features/About/AboutView.swift

@@ -28,16 +28,13 @@ struct AboutView: View {
 
     var body: some View {
         VStack(spacing: 16) {
-            if let appIcon = NSImage(named: "AppIcon") {
-                Image(nsImage: appIcon)
-                    .resizable()
-                    .frame(width: 80, height: 80)
-            } else {
-                Image(systemName: "text.book.closed.fill")
-                    .font(.system(size: 48))
-                    .foregroundStyle(Color.accentColor)
-                    .frame(width: 80, height: 80)
-            }
+            // `NSImage(named: "AppIcon")` doesn't reliably resolve an App
+            // Icon asset-catalog entry on macOS — `NSApp.applicationIconImage`
+            // is the API that's actually guaranteed to match what the Dock
+            // and Finder show for the running app.
+            Image(nsImage: NSApp.applicationIconImage)
+                .resizable()
+                .frame(width: 80, height: 80)
 
             VStack(spacing: 4) {
                 Text(appName)