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/schema/ui_schema.cpp

@@ -45,6 +45,7 @@ bool UISchema::loadFromFile(const std::string& path) {
 
     // Clear previous data
     elements_.clear();
+    styleCache_.clear();
     backgroundImagePath_.clear();
     logoImagePath_.clear();
 
@@ -92,6 +93,7 @@ bool UISchema::loadFromFile(const std::string& path) {
     overlayPath_.clear(); // No overlay yet
     loaded_ = true;
     dirty_ = false;
+    ++generation_;
 
     // Record initial modification time
     try {
@@ -126,6 +128,7 @@ bool UISchema::loadFromString(const std::string& tomlStr, const std::string& lab
 
     // Clear previous data
     elements_.clear();
+    styleCache_.clear();
     backgroundImagePath_.clear();
     logoImagePath_.clear();
 
@@ -222,6 +225,7 @@ bool UISchema::mergeOverlayFromFile(const std::string& path) {
     // Track overlay file for hot-reload
     currentPath_ = path;
     ++generation_;
+    styleCache_.clear();  // Invalidate after overlay merges new elements
     try {
         lastModTime_ = std::filesystem::last_write_time(path);
     } catch (const std::filesystem::filesystem_error&) {}
@@ -495,6 +499,9 @@ void UISchema::applyIfDirty() {
     if (!dirty_) return;
     dirty_ = false;
 
+    // Clear style cache before snapshot so we re-read from TOML
+    styleCache_.clear();
+
     // Snapshot font sizes before reload for change detection
     static const char* fontKeys[] = {
         "h1", "h2", "h3", "h4", "h5", "h6",
@@ -513,10 +520,17 @@ void UISchema::applyIfDirty() {
 
     DEBUG_LOGF("[UISchema] Hot-reload: re-parsing %s\n", currentPath_.c_str());
 
+    // Save overlay path before reloading — loadFromFile/loadFromString clear it
+    std::string savedOverlay = overlayPath_;
+
     // If an overlay is active, reload base first then re-merge overlay
-    if (!overlayPath_.empty() && !basePath_.empty()) {
+    if (!savedOverlay.empty() && !basePath_.empty()) {
         loadFromFile(basePath_);
-        mergeOverlayFromFile(overlayPath_);
+        mergeOverlayFromFile(savedOverlay);
+    } else if (!savedOverlay.empty() && !embeddedTomlStr_.empty()) {
+        // Embedded base (e.g. Windows single-file): reload from stored string
+        loadFromString(embeddedTomlStr_, "embedded-reload");
+        mergeOverlayFromFile(savedOverlay);
     } else {
         loadFromFile(currentPath_);
     }
@@ -836,15 +850,26 @@ SeparatorStyle UISchema::separator(const std::string& section, const std::string
     return result;
 }
 
-DrawElementStyle UISchema::drawElement(const std::string& section, const std::string& name) const {
-    DrawElementStyle result;
+const DrawElementStyle& UISchema::drawElement(const std::string& section, const std::string& name) const {
+    static const DrawElementStyle s_empty{};
 
-    const void* elem = findElement(section, name);
-    if (elem) {
-        detail::parseDrawElementStyle(elem, result);
+    std::string key = section + "." + name;
+
+    // Return from cache if already parsed
+    auto cit = styleCache_.find(key);
+    if (cit != styleCache_.end()) {
+        return cit->second;
     }
 
-    return result;
+    // Parse from TOML and cache
+    const void* elem = findElement(section, name);
+    if (!elem) {
+        return s_empty;
+    }
+
+    auto [it, _] = styleCache_.emplace(std::move(key), DrawElementStyle{});
+    detail::parseDrawElementStyle(elem, it->second);
+    return it->second;
 }
 
 } // namespace schema

src/ui/schema/ui_schema.h

@@ -255,8 +255,12 @@ public:
 
     /**
      * @brief Look up a DrawList custom element style
+     *
+     * Returns a cached const reference. The cache is invalidated on
+     * hot-reload (applyIfDirty) and full loads. For missing elements
+     * a static empty sentinel is returned.
      */
-    DrawElementStyle drawElement(const std::string& section, const std::string& name) const;
+    const DrawElementStyle& drawElement(const std::string& section, const std::string& name) const;
 
     /**
      * @brief Find a raw stored element by section and name.
@@ -365,6 +369,10 @@ private:
         std::any data;  // holds toml::table at runtime
     };
     std::unordered_map<std::string, StoredElement> elements_;
+
+    // Parsed DrawElementStyle cache — avoids repeated TOML table iteration.
+    // Populated lazily on first drawElement() lookup, cleared on reload.
+    mutable std::unordered_map<std::string, DrawElementStyle> styleCache_;
 };
 
 // Convenience alias