docs: add comprehensive run instructions for Grok2API (local, Docker Compose, Docker, and image build)

[cto-new]

Summary

This PR adds a comprehensive environment run guide to the README, covering local development, Docker Compose deployment, standalone Docker run, and building a custom image. It also documents Cloudflare WARP auto-install behavior and clarifies port usage and access URLs. The update aligns with the existing GitHub Actions workflow that builds and publishes Docker images to GHCR.

Details

• Replaced the previous "如何部署" with a new "如何运行环境" section.
• Added step-by-step local development instructions (virtualenv, dependencies, env vars) and how to start services on port 8000 or 8001 as appropriate.
• Documented Docker Compose deployment with storage mode and port mappings.
• Documented standalone Docker run and instructions for building Docker images.
• Clarified port usage differences: local development uses port 8001 (for main.py) or 8000 (uvicorn); Docker uses 8000; updated access URLs accordingly.
• Summarized WARP auto-install behavior and related configuration notes.
• Added a GitHub Actions section describing automated Docker image builds to GHCR with multi-arch support (amd64 and arm64), including trigger conditions (push to main, version tags vX.Y.Z, and PR builds for validation), tagging rules, and how to pull images.
• Ensured no breaking changes; no security changes; documentation-only update.