[codex] Improve GitHub About and README readability

[RayLi-Muye]

Closes #4.

Scope

• Reworked README.md so first-time developers can quickly understand the repository purpose, stack, local setup, commands, structure, SEO/metadata maintenance boundaries, deployment boundary, contribution workflow, and documentation map.
• Added a docs/DEVELOPMENT_LOG.md entry for the README/About refresh.
• Updated GitHub About metadata with neutral developer-facing wording.

GitHub About metadata changed

• description: from official Website of Mist Architect to Developer repository for the MIST Architects bilingual portfolio website.
• homepage: from https://mist-architect-web.vercel.app to https://mist-arch.com
• topics: from none to nextjs, react, typescript, architecture-portfolio, bilingual-site, playwright, github-actions, alibaba-cloud

Verification

• git diff --check
• GitHub Actions CI should run on this PR.

Docs impact

• README becomes the first-stop developer overview.
• Development log records the repository metadata and README refresh.

Risk / rollback

• Runtime risk is low: this PR only changes repository documentation.
• GitHub About metadata can be rolled back with gh repo edit if needed.
• No website runtime UI, SEO metadata, brand copy, visual direction, preview deploy, production deploy, Bing/Webmaster state, or customer-visible site behavior changed.

Owner decision needs

• Confirm whether the new README structure and GitHub About metadata should be kept.
• Merge/deploy decisions remain owner-controlled; this PR itself does not require a site deployment beyond normal source control policy.