fix: Communication page, search field mapping, type compatibility

- Create Communication.tsx page with tree structure (System, KI, Kollegen)
- Chat window with messages, reactions, attachments, mini-apps
- WebSocket real-time updates
- AI streaming integration for AI conversations
- Fix search.ts: map backend fields (entity_type/entity_id/title/snippet)
  to frontend format (type/id/name/description/url)
- Fix hooks.ts: import SearchResult from search.ts instead of redefining
- Fix JSX syntax error in Communication.tsx title attribute

frontend/src/api/hooks.ts

@@ -24,13 +24,8 @@ export * from './automation';
 
 // ── Search hook (uses dynamic import, kept inline) ──
 
-export interface SearchResult {
-  type: 'company' | 'contact' | 'mail' | 'file' | 'event';
-  id: string;
-  name: string;
-  description?: string;
-  url: string;
-}
+import type { SearchResult } from './search';
+export type { SearchResult };
 
 export function useGlobalSearch(query: string, entityTypes?: string[]) {
   return useQuery({