feat: add first SDK implementation

[AdirAmsalem]

Add Python SDK for Decart API

Implements a fully-featured Python SDK for Decart, enabling video and image generation/transformation and real-time communication.
Aligned with the Python SDK documentation.

Usage

import asyncio
import os
from decart_sdk import DecartClient, models

async def main():
    async with DecartClient(api_key=os.getenv("DECART_API_KEY")) as client:
        result = await client.process({
            "model": models.video("lucy-pro-t2v"),
            "prompt": "A serene lake at sunset",
        })

        with open("output.mp4", "wb") as f:
            f.write(result)

asyncio.run(main())