feat(mac): About window — changelog link + update discovery (+ website /changelog)

[oratis]

What

A version-upgrade mechanism on the Mac app's About screen: jump to the meetlisa.ai changelog, and discover + download new versions. Plus the branded changelog page the link points to.

Mac app (packaging/mac-client)

• Updater.swift — dependency-free discovery: GET the latest GitHub release, semver-compare to the bundle version, surface the notarized DMG asset (or release page). Launch discovery is throttled to once/day and once per version (never nags).
  • Deliberately not Sparkle: it discovers + opens the download (Gatekeeper verifies the notarized DMG) rather than hand-rolling an in-place binary swap — the RCE surface we don't want to own. (Sparkle = a clean future upgrade if one-click in-place is wanted.)
• AboutWindow.swift — custom About window (replaces the standard panel): icon / name / version / MIT link, a "Changelog" button → meetlisa.ai/changelog, and an in-place "Check for Updates" → "Download vX" flow with status text.
• AppDelegate — About menu opens the custom window; new "Check for Updates…" menu item; quiet launch discovery shows a gentle Download / Changelog / Later prompt only when a newer release exists. Info.plist fallback → 0.10.0 (the build still stamps the real version from package.json).

Website (so the link resolves)

• /changelog (+ /zh-CN/changelog) — built from the GitHub Releases API at build time (fail-safe → GitHub fallback), rendered as terminal cards matching the site's CRT aesthetic. lib/releases.ts is the shared fetch. Nav gains "changelog" in both languages.

Verification

• swift build — clean (Swift 6.3.2)
• npm run build (website) — /changelog + /zh-CN/changelog render 10 real release cards (v0.10.0 → v0.2.0), no fallback
• Behavior choices noted inline: open-download (not in-place auto-update); daily/once-per-version discovery

Note: the live meetlisa.ai/changelog page appears on the next website deploy; the app link is correct immediately.

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