feat: Add thinking indicator during bot response generation

UX improvement: Show loading state while generating response

✨ Enhancement:
- Display "🤔 응답 생성 중..." message immediately after user input
- Replaced by actual bot response when generation completes
- Improves user feedback during wait time

🎯 User Experience Flow:
1. User sends message → Message displays instantly
2. "🤔 응답 생성 중..." appears → User knows bot is working
3. Bot response ready → Thinking indicator replaced with response

📝 Implementation:
- Added intermediate yield with thinking indicator
- Three-stage generator: user message → thinking → response
- Clear visual feedback throughout entire process

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

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

app.py

@@ -226,9 +226,12 @@ with gr.Blocks(title="🤖 Llama-2-Ko Chatbot") as demo:
     def submit(message, history):
         # Immediately show user message
         updated_history = history + [{"role": "user", "content": message}]
-        # Return updated history first (shows user message immediately)
-        # Then generate bot response
         yield updated_history, ""
+
+        # Show "thinking" indicator
+        thinking_history = updated_history + [{"role": "assistant", "content": "🤔 응답 생성 중..."}]
+        yield thinking_history, ""
+
         # Generate and add bot response
         final_history = chat_wrapper(message, history)
         yield final_history, ""