Add examples/async_usage.py with:
- Simple async chat completion
- Async streaming with aiter_lines()
- Chat with context using chatId
- Get chat histories asynchronously
- Get app analytics
- Multiple concurrent requests with asyncio.gather()
- Chat with template variables
- Get chat records
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
