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/data/wallet_state.h

@@ -162,6 +162,9 @@ struct PoolMiningState {
     int64_t memory_used  = 0;
     int     threads_active = 0;
 
+    // Pool-side hashrate (from pool stats API)
+    double pool_hashrate = 0;
+
     // Hashrate history for chart (mirrors MiningInfo::hashrate_history)
     std::vector<double> hashrate_history;
     static constexpr int MAX_HISTORY = 60; // 5 minutes at ~5s intervals