i18n(mining): route xmrig updater strings through TR()

Replace the English string literals in the miner-update dialog + the "Update miner…" mining-tab
button/tooltip with TR() keys, and register their English text in i18n.cpp's loadBuiltinEnglish()
(the in-code English fallback that non-English locales overlay). Reuses the existing cancel/close/
retry keys. Labeled values use a "%s %s" literal format with a TR'd label (no -Wformat-security
risk). Non-English locales fall back to English for the new xmrig_* keys until translations are
added to res/lang/*.json.

Both variants build; suite passes; hygiene clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/mining_tab.cpp

@@ -1582,11 +1582,11 @@ static void RenderMiningTabContent(App* app)
     if (s_pool_mode) {
         const bool minerBusy = state.pool_mining.xmrig_running;
         ImGui::BeginDisabled(minerBusy);
-        if (TactileButton("Update miner…", ImVec2(availWidth, 0)))
+        if (TactileButton(TR("xmrig_update_button"), ImVec2(availWidth, 0)))
             XmrigDownloadDialog::show(app);
         ImGui::EndDisabled();
         if (minerBusy && ImGui::IsItemHovered(ImGuiHoveredFlags_AllowWhenDisabled))
-            ImGui::SetTooltip("Stop mining before updating the miner.");
+            ImGui::SetTooltip("%s", TR("xmrig_stop_mining_first"));
         ImGui::Dummy(ImVec2(0, gap));
     }