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/qr_popup_dialog.cpp

@@ -4,6 +4,7 @@
 
 #include "qr_popup_dialog.h"
 #include "../../app.h"
+#include "../../util/i18n.h"
 #include "../widgets/qr_code.h"
 #include "../schema/ui_schema.h"
 #include "../material/draw_helpers.h"
@@ -63,7 +64,7 @@ void QRPopupDialog::render(App* app)
     auto addrInput = S.input("dialogs.qr-popup", "address-input");
     auto actionBtn = S.button("dialogs.qr-popup", "action-button");
 
-    if (material::BeginOverlayDialog("QR Code", &s_open, win.width, 0.94f)) {
+    if (material::BeginOverlayDialog(TR("qr_title"), &s_open, win.width, 0.94f)) {
         
         // Label if present
         if (!s_label.empty()) {
@@ -86,7 +87,7 @@ void QRPopupDialog::render(App* app)
         } else {
             // Fallback: show error
             ImGui::BeginChild("QRPlaceholder", ImVec2(qr_size, qr_size), true);
-            ImGui::TextWrapped("Failed to generate QR code");
+            ImGui::TextWrapped("%s", TR("qr_failed"));
             ImGui::EndChild();
         }
         
@@ -95,7 +96,7 @@ void QRPopupDialog::render(App* app)
         ImGui::Spacing();
         
         // Address display
-        ImGui::Text("Address:");
+        ImGui::Text("%s", TR("address_label"));
         
         // Use multiline for z-addresses
         if (s_address.length() > 50) {
@@ -120,13 +121,13 @@ void QRPopupDialog::render(App* app)
         float start_x = (window_width - total_width) / 2.0f;
         ImGui::SetCursorPosX(start_x);
         
-        if (material::StyledButton("Copy Address", ImVec2(button_width, 0), S.resolveFont(actionBtn.font))) {
+        if (material::StyledButton(TR("copy_address"), ImVec2(button_width, 0), S.resolveFont(actionBtn.font))) {
             ImGui::SetClipboardText(s_address.c_str());
         }
         
         ImGui::SameLine();
         
-        if (material::StyledButton("Close", ImVec2(button_width, 0), S.resolveFont(actionBtn.font))) {
+        if (material::StyledButton(TR("close"), ImVec2(button_width, 0), S.resolveFont(actionBtn.font))) {
             close();
         }
         material::EndOverlayDialog();