feat(koplugin): add i18n catalog and sync info dialog (#4050)

- i18n loader at apps/readest.koplugin/i18n.lua: isolated callable,
  falls back to KOReader's gettext when a string is untranslated
- Translation catalog at locales/<i18next-code>/translation.po for 31
  languages, mirroring apps/readest-app/public/locales/
- scripts/extract-i18n.js (scan _("...") and _([[...]]); preserve
  existing, drop obsolete, add new) and scripts/apply-translations.js
  (bulk import from /tmp/koplugin-translations/<lang>.json)
- Mirror apps/readest-app SyncInfoDialog: rename showMetaHashInfo to
  showSyncInfo, dialog title "Sync Info", new Last Synced row computed
  as max(last_synced_at_config, last_synced_at_notes) from doc_settings
- syncconfig.lua / syncannotations.lua mark per-book sync timestamps
  on push/pull success
- Rename "Meta Hash" -> "Book Fingerprint" in koplugin and
  apps/readest-app SyncInfoDialog.tsx; translations propagated to
  all readest-app locales
- "book config" -> "reading progress" wording across user-facing
  strings (matches QiuYukang fork terminology)
- Replace "Log out as " / "Login failed: " concat prefixes with
  T(_("...%1..."), arg) placeholder pattern (RTL / verb-final friendly)
- pnpm lint:lua: luajit -b syntax check across koplugin .lua files;
  soft-skips when luajit is missing locally; CI installs luajit and
  runs the check unconditionally

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/readest-app/.claude/memory/MEMORY.md

@@ -20,6 +20,7 @@
 - [D-pad Navigation](dpad-navigation.md) — Android TV remote / keyboard arrow navigation design, key files, and pitfalls
 - [Cloudflare Workers WebSocket](cloudflare-workers-websocket.md) — use fetch() Upgrade pattern (not `ws` npm); CF delivers binary frames as Blob (must serialize async decodes)
 - [Share-a-Book Feature (in progress)](share-feature.md) — locked decisions for the /s/{token} share-link feature; plan at ~/.claude/plans/ok-we-will-learn-cosmic-acorn.md
+- [readest.koplugin i18n](koplugin-i18n.md) — gettext loader at `apps/readest.koplugin/i18n.lua`, `.po` catalog at `locales/<i18next-code>/translation.po`, extract/apply scripts in `scripts/`
 
 ## Patterns
 - [Virtuoso + OverlayScrollbars](virtuoso_overlayscrollbars.md) — useOverlayScrollbars hook integration for overlay scrollbars on mobile webviews