Fix API key usage: use agentServerApiKey for agent server authentication

- Changed ConversationManager to use settings.agentServerApiKey instead of settings.apiKey
- Updated useEffect dependency to watch for agentServerApiKey changes
- Keeps settings.apiKey for LLM authentication in agent creation
- Resolves issue where x-session-api-key header was incorrectly set with LLM key

This ensures proper separation between:
- agentServerApiKey: for authenticating with the OpenHands agent server
- apiKey: for LLM API calls within agent configurations

Author: openhands-agent

example/src/components/ConversationManager.tsx

@@ -33,12 +33,12 @@ export const ConversationManager: React.FC = () => {
     if (settings.agentServerUrl) {
       const conversationManager = new SDKConversationManager({
         host: settings.agentServerUrl,
-        apiKey: settings.apiKey
+        apiKey: settings.agentServerApiKey
       });
       setManager(conversationManager);
       loadConversations(conversationManager);
     }
-  }, [settings.agentServerUrl, settings.apiKey]);
+  }, [settings.agentServerUrl, settings.agentServerApiKey]);
 
   const loadConversations = async (conversationManager?: SDKConversationManager) => {
     const mgr = conversationManager || manager;