chore: hide update + changelog + feedback UI

[aletc1]

Summary

Temporarily disables all update-related and feedback UI entry points in the app. All original implementation is preserved verbatim behind UPDATES-DISABLED markers — grep for UPDATES-DISABLED across src/ to find every commented block and uncomment to reactivate.

What's hidden

• macOS app menu → removed "Check for Updates..." / "Update to vX..." item
• Main process → auto-updater init, IPC handlers (update:*), 5s startup check, window-focus check
• Preload bridge → checkForUpdates, downloadUpdate, installUpdate, setUpdateChannel, getUpdateChannel, all onUpdate* event listeners
• Update banner (bottom-left) → component returns null; useUpdateChecker() no longer called in layout
• Settings → Beta tab → entire "Updates" section (Early Access toggle + Check Now button + version display)
• Help popover → "What's new" changelog section + release highlights fetch (no more GET /api/changelog/desktop)
• Sidebar → "Feedback" button

Not changed

• Build/release pipeline (package.json publish config, scripts/generate-update-manifest.mjs) — release artifacts still publish normally
• electron-updater dependency — kept installed; removing would break compilation of the (preserved) source
• Update-related atoms and hooks — no longer invoked, left untouched for clean reactivation

Test plan

• bun run dev → launch app, verify:
  • 1Code menu shows About → Settings → CLI → Services → Hide → Quit (no "Check for Updates...")
  • Settings → Beta tab shows only Rollback / Offline Mode / Automations (no Updates section)
  • Help popover (sidebar ?) shows only Discord + Shortcuts (no "What's new", no "Full changelog")
  • No bottom-left update banner on startup or window focus
  • No Feedback button at bottom of sidebar
  • DevTools → Network: no requests to cdn.21st.dev/releases/* or 21st.dev/api/changelog/desktop
• bun run build passes clean
• bun run package:mac → open packaged .app, confirm none of the above appear

Reactivation

rg UPDATES-DISABLED src/