fix(apple): title the app "Punktfunkempfänger" — navigation title + window title

Matches the bundle display name; was the lowercase project name "punktfunk" in the
home navigation title (iOS large title / macOS titlebar) and the WindowGroup title.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/PunktfunkClientApp.swift

@@ -13,7 +13,7 @@ struct PunktfunkClientApp: App {
     #endif
 
     var body: some Scene {
-        WindowGroup("punktfunk") {
+        WindowGroup("Punktfunkempfänger") {
             ContentView()
         }
         #if os(macOS)