feat: Full UI internationalization, pool hashrate stats, and layout caching

- Replace all hardcoded English strings with TR() translation keys across
  every tab, dialog, and component (~20 UI files)
- Expand all 8 language files (de, es, fr, ja, ko, pt, ru, zh) with
  complete translations (~37k lines added)
- Improve i18n loader with exe-relative path fallback and English base
  fallback for missing keys
- Add pool-side hashrate polling via pool stats API in xmrig_manager
- Introduce Layout::beginFrame() per-frame caching and refresh balance
  layout config only on schema generation change
- Offload daemon output parsing to worker thread
- Add CJK subset fallback font for Chinese/Japanese/Korean glyphs

src/ui/windows/console_tab.h

@@ -119,6 +119,7 @@ private:
     size_t last_xmrig_output_size_ = 0;
     bool shown_startup_message_ = false;
     daemon::EmbeddedDaemon::State last_daemon_state_ = daemon::EmbeddedDaemon::State::Stopped;
+    bool last_rpc_connected_ = false;
     
     // Text selection state
     bool is_selecting_ = false;