docs: add VitePress GitHub Pages site

[orangeboyChen]

Summary

• add an independent VitePress documentation site under docs/
• add a GitHub Pages workflow that builds and deploys only docs/.vitepress/dist
• document Docker, local setup, storage choices, and the separation from the server image
• ignore VitePress dependencies and generated output in the main app lint/test scans

Verification

• bun run lint ✅
• bun run format:check ✅
• bun run typecheck ✅
• bun run test:coverage ✅ (94.39% lines)
• bun run build in docs/ ✅
• bun run build (main Next.js app) ⚠️ Turbopack fails in this environment while binding a port during CSS processing

[chatgpt-codex-connector]

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Reviewed commit: 03f4a7f9ec

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.77%. Comparing base (eb951f7) to head (e0e1876).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #100   +/-   ##
=======================================
  Coverage   94.77%   94.77%           
=======================================
  Files          21       21           
  Lines        4251     4251           
  Branches     1238     1238           
=======================================
  Hits         4029     4029           
  Misses        222      222           

Flag	Coverage Δ
unittests	94.77% <ø> (ø)

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