Remove API key functionality from application

Enhance API key functionality with regeneration and better management

Update model from qwen3:4b to qwen3:1.7b

Add API key authentication and tech specifications document

feat: Change model to qwen3:4b

feat: Change model to qwen3:8b

feat: Implement streaming response for chat

fix: Correct model name to qwen3:1.7b

feat: Change model to qwen:1.5b

refactor: Simplify main.py for debugging

feat: Use qwen3:4b model

fix: Change chat endpoint to /chat_api and add /hello

fix: Reorder endpoints to fix 404 error on /api/chat

feat: Add /hello endpoint for debugging

feat: Add chat interface and versioned API

feat: Add FastAPI gateway for API key authentication