Update app.py

app.py

@@ -26,7 +26,7 @@ def generate_caption(image_base64, api_key):
     api_url = "https://api.studio.nebius.ai/v1/chat/completions"
     headers = {"Authorization": f"Bearer {api_key}"}
     payload = {
-        "model": "Qwen/Qwen2-VL-7B-Instruct",
+        "model": "mistralai/Mistral-Small-3.1-24B-Instruct-2503",
         "messages": [
             {"role": "system", "content": "You are an image-to-text prompt converter for AI image generation."},
             {"role": "user", "content": [