fix(UI-Overhaul-Phase1): 7 Bugs behoben

1.1 Contacts refresh: useUnifiedContacts mutations already invalidate (verified)
1.2 Contacts drag-drop: ContactList items already draggable + ContactFolderTree onDrop (verified)
1.3 Contacts move dialog: Added move-to-folder dropdown in ContactDetail
1.4 Wiki save refresh: Added refreshKey prop to WikiBrowser, triggers reload after save/delete
1.5 Calendar dialog close: Window.tsx now injects windowId into componentProps
1.6 Communication AI chat: Added metadata support to ConversationCreate schema + service,
    frontend passes conversation_type metadata for AI/system chats,
    categorization checks metadata first
1.7 Wiki duplicate menu: Removed hardcoded /wiki from Sidebar.tsx (plugin provides it dynamically)

Backend: kommunikation schema/routes/services updated for metadata support
Frontend: tsc clean, build successful

frontend/src/components/layout/Sidebar.tsx

@@ -54,7 +54,6 @@ function getIcon(name: string): React.ReactNode {
 const singleItems: NavSingleItem[] = [
   { to: '/dashboard', labelKey: 'nav.dashboard', icon: <Home className="w-5 h-5 flex-shrink-0" aria-hidden="true" strokeWidth={2} />, order: 0 },
   { to: '/contacts', labelKey: 'nav.contacts', icon: <Users className="w-5 h-5 flex-shrink-0" aria-hidden="true" strokeWidth={2} />, order: 10 },
-  { to: '/wiki', labelKey: 'nav.wiki', icon: <BookOpen className="w-5 h-5 flex-shrink-0" aria-hidden="true" strokeWidth={2} />, order: 30 },
   { to: '/system-dashboard', labelKey: 'nav.systemDashboard', icon: <Activity className="w-5 h-5 flex-shrink-0" aria-hidden="true" strokeWidth={2} />, order: 90 },
 ];