fix: Disable AI chat streaming to use working non-streaming endpoint

- Change useStreaming default from true to false
- Streaming endpoint has validation issues (conversationId format)
- Non-streaming endpoint works perfectly
- This fixes the 'Sorry, I encountered an error' message in AI chat

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/components/features/ai-chat/AIChatInterface.tsx

@@ -92,7 +92,7 @@ export const AIChatInterface: React.FC = () => {
   const [input, setInput] = useState('');
   const [isLoading, setIsLoading] = useState(false);
   const [streamingMessage, setStreamingMessage] = useState('');
-  const [useStreaming, setUseStreaming] = useState(true); // Toggle for streaming
+  const [useStreaming, setUseStreaming] = useState(false); // Disable streaming for now - using non-streaming endpoint
   const [currentThinkingMessages, setCurrentThinkingMessages] = useState<string[]>([]);
   const [currentThinkingIndex, setCurrentThinkingIndex] = useState(0);
   const [conversations, setConversations] = useState<Conversation[]>([]);