chore: update model endpoint to deepseek-ai/DeepSeek-V4-Pro:fireworks-ai

refactor: switch model to fastest and format CSS in index.html

Update app.py

refactor: remove explicit output definition and update chat return type hint

feat: specify text output format in chat api decorator

refactor: remove explicit path from chat API route decorator

feat: initialize DeepSeek V4 Pro project with a Gradio-backed web chat interface