Enhance APIRequestBuilder: Add JSON escaping for system and user promt

[longshuicy]

To test:
Type "" and enter in the API query builder.
You should get something like below:

curl -X POST http://localhost:3000/api/chat-api/chat \
  -H "Content-Type: application/json" \
  -d '{
    "model": "Qwen/Qwen2.5-VL-72B-Instruct",
    "messages": [
      {
        "role": "system",
        "content": "You are a helpful AI assistant. Follow instructions carefully. Respond using markdown.\nlalala\nlalala\ntest \"test\"\ntest \\n test"
      },
      {
        "role": "user",
        "content": "What is in these documents?"
      }
    ],
    "api_key": <YOUR API KEY>,
    "course_name": "chat",
    "stream": false,
    "temperature": 0.1,
    "retrieval_only": false
  }'

Test the curl and you should expect to see results back

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Project	Deployment	Actions	Updated (UTC)
uiuc-chat-frontend	Building	Preview, Comment	Feb 26, 2026 6:31pm

[rohan-uiuc]

\n works fine. Do we want to handle quotes(', ") too? For example go here and try the curl, it will break due to ' in the system prompt. Also, I would encourage adding a test for that use case.