Add Mistral AI integration - 1B tokens/month (33x Groq limits)

fix: Support follow-up requests without re-uploading file

feat: Add dynamic prompt system for small context window models (Groq support)

fix: Support both GOOGLE_API_KEY and GEMINI_API_KEY env vars for HuggingFace compatibility

fix: Remove system_instruction parameter from chat endpoint

fix: Fix module import paths for Render deployment

fix: Resolve blank modal issue when viewing YData Profiling reports

feat: Initial commit - Data Science Agent with React frontend and FastAPI backend