[WIP] Sphinx-style Documentation Setup

[Strivin0311]

🗂️ PR Category

• ✨ New Feature
• 🚀 Optimization (performance, memory, etc.)
• 💥 Breaking Change
• 🐛 Bug Fix
• 🛠️ Development / Refactoring
• 📚 Documentation
• 🧹 Chore (Dependencies, CI/CD, Configuration, etc.)
• 🧪 Testing

📝 Description

This PR bootstraps a bilingual (English + 简体中文) Sphinx documentation site for MagiCompiler, along with the CI workflow to deploy it to GitHub Pages. No source code, README, or existing CI is touched.

Docs toolchain & build

• docs/requirements.txt — Sphinx + pydata-sphinx-theme + myst-parser + ablog + i18n deps.
• docs/Makefile / docs/make.bat — build targets including html-en, html-zh, html-multilang, and update-po.
• .github/workflows/sphinx.yaml — builds English (site root) + Chinese (zh_CN/) and deploys to the gh-pages branch under docs/main.

Sphinx sources (docs/source/)

• conf.py, index.md, custom CSS, and a language switcher template (English at root, Chinese under zh_CN/).
• user_guide/ — starter pages (install, quickstart) forked/adapted from the current README.
• blog/ — three technical posts ported from the existing docs/*.md (why_magi_depyf, auto_cpu_offload, auto_cuda_graph_design) as ablog posts. Raw-HTML <img> blocks were converted to MyST {image} directives so assets are copied and paths resolve on the built site.

Internationalization

• docs/README.md / README_zh.md — contributor guide for building/writing/translating docs.
• docs/locale/zh_CN/LC_MESSAGES/*.po — full Chinese translations for all pages (UI strings, guides, and the three blog posts); code blocks, API names, commands, and URLs are kept verbatim.

Verification: make html-multilang builds both languages with zero warnings; the Chinese site renders translated content and the EN ⇄ 中文 switcher resolves correctly.

[jiahy0825]

LGTM