feat: iOS Datenebene + Ersteller-Anzeige + Privat-Flag

- Modelle: CalEvent (creator, isPrivate, owner, isGroupEvent, displayColor),
  LocalCalendar (owned/sharedBy/permission/group), AppSettings
  (privateEventVisibility, groupVisibleCalendarId), UserProfile (displayName);
  neue Modelle CalGroup/GroupMember/DirectoryUser/CalendarShare.
- API: Profil-Update (Name/Login), Sharing-CRUD, Gruppen-CRUD + combined,
  Mitglieder-Farbe, iCal Import (multipart) & Export, private-Flag bei Events.
- Event-Detail zeigt "Erstellt von" (wenn != ich) + Privat-Hinweis;
  Editor hat Privat-Toggle (nur lokale Kalender). Login speichert userId.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Calendarr iOS/Views/Calendar/EventDetailSheet.swift

@@ -47,6 +47,11 @@ struct EventDetailSheet: View {
 
     private var canDelete: Bool { canEdit }
 
+    private var currentUserId: Int? {
+        let id = UserDefaults.standard.integer(forKey: "userId")
+        return id == 0 ? nil : id
+    }
+
     var body: some View {
         NavigationStack {
             List {
@@ -91,6 +96,18 @@ struct EventDetailSheet: View {
                         Text(event.source.capitalized)
                             .foregroundStyle(.secondary)
                     }
+                    if let creator = event.creator, creator.id != currentUserId {
+                        HStack {
+                            Label("Erstellt von", systemImage: "person")
+                            Spacer()
+                            Text(creator.displayName)
+                                .foregroundStyle(.secondary)
+                        }
+                    }
+                    if event.isPrivate {
+                        Label("Privat", systemImage: "lock")
+                            .foregroundStyle(.secondary)
+                    }
                 }
 
                 if !store.writableCalendars.isEmpty {