refactor(audit): batch 4 — UI design-system helpers + i18n

Mechanical, behavior-preserving consolidations from the audit. Rendering
extractions were kept byte-equivalent; sites that couldn't be made identical
were left as-is (noted below).

Shared helpers:
- util::truncateMiddle(s,maxLen) / (s,front,back) in text_format.h — replaces
  6 file-local middle-ellipsis truncators + several inline substr sites
  (send/receive/transactions/balance_recent_tx/explorer + app.cpp + 3 dialogs).
  Carries the maxLen<=3 guard, fixing the latent unsigned-underflow copies.
- material::LoadingDots() in draw_helpers.h — one animated-ellipsis source for
  8 copy-pasted spinner sites (identical GetTime()*3 phase preserved).
- Reuse the existing FormatHashrate() in explorer_tab + peers_tab (dropped two
  inline hashrate ladders).
- material::DrawButtonGlassOverlay() — the glass-fill/rim/tactile overlay block
  shared by TactileButton / TactileSmallButton / schema TactileButton.
- material::CollapsibleHeader() — the invisible-button + label + chevron idiom
  (3 of 5 settings_page sites; RPC/Debug headers skipped — non-identical).
- material::GlassCardScope (RAII) — the ChannelsSplit/Indent/DrawGlassPanel/
  ChannelsMerge card scaffold (5 settings_page cards; About/send/receive skipped
  — different padding / logo interleaving).
- material::DialogWarningHeader()/DialogConfirmFooter() — warning header +
  50/50 Cancel/danger footer across the confirm dialogs; button height moved
  from a hardcoded 40px into ui.toml (components.overlay-dialog.confirm-btn-height).
- File-local enterLowSpec()/exitLowSpec() collapse the 3 low-spec snapshot copies.

i18n: wrapped hardcoded English in the shared balance render paths and the
whole Lite lifecycle/security section in TR(), with English defaults added to
loadBuiltinEnglish() (res/lang/*.json left for the translation tooling — TR
falls back to English, so output is unchanged).

Full-node + Lite build clean; ctest 1/1; hygiene clean. These are rendering
changes — the Settings page (cards/headers/confirm dialogs), all tactile
buttons, and the Lite settings section warrant a screenshot check.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/send_tab.cpp

@@ -147,14 +147,6 @@ static double GetAvailableBalance(App* app) {
     return 0.0;
 }
 
-static std::string TruncateAddress(const std::string& addr, size_t maxLen = 40) {
-    // Guard maxLen <= 3 before the unsigned (maxLen - 3): otherwise it wraps and the
-    // trailing substr(length - halfLen) throws std::out_of_range on short inputs.
-    if (maxLen <= 3 || addr.length() <= maxLen) return addr;
-    size_t halfLen = (maxLen - 3) / 2;
-    return addr.substr(0, halfLen) + "..." + addr.substr(addr.length() - halfLen);
-}
-
 // Recipient validity = prefix/length pre-filter AND a real encoding-checksum check, so a
 // transcription error that still matches the prefix/length is no longer labelled "Valid".
 // The checksum verifiers are version-agnostic, so they never reject a genuine address.
@@ -256,8 +248,8 @@ static void RenderSourceDropdown(App* app, float width) {
         const auto& addr = state.addresses[s_selected_from_idx];
         bool isZ = addr.type == "shielded";
         const char* tag = isZ ? "[Z]" : "[T]";
-        std::string trunc = TruncateAddress(addr.address,
-            static_cast<size_t>(std::max(S.drawElement("tabs.send", "addr-preview-trunc-min").size, width / S.drawElement("tabs.send", "addr-preview-trunc-divisor").size)));
+        std::string trunc = util::truncateMiddle(addr.address,
+            static_cast<int>(std::max(S.drawElement("tabs.send", "addr-preview-trunc-min").size, width / S.drawElement("tabs.send", "addr-preview-trunc-divisor").size)));
         snprintf(buf, sizeof(buf), "%s %s  —  %.8f %s",
                  tag, trunc.c_str(), addr.balance, DRAGONX_TICKER);
         s_source_preview = buf;
@@ -287,7 +279,7 @@ static void RenderSourceDropdown(App* app, float width) {
                     bool isZ = addr.type == "shielded";
                     const char* tag = isZ ? "[Z]" : "[T]";
 
-                    std::string trunc = TruncateAddress(addr.address, addrTruncLen);
+                    std::string trunc = util::truncateMiddle(addr.address, (int)addrTruncLen);
                     snprintf(buf, sizeof(buf), "%s %s  —  %.8f %s",
                              tag, trunc.c_str(), addr.balance, DRAGONX_TICKER);
 
@@ -347,7 +339,7 @@ static void RenderAddressSuggestions(const WalletState& state, float width, cons
     ImGui::BeginChild(childId, ImVec2(width, sugH), true);
     for (size_t si = 0; si < suggestions.size(); si++) {
         int sugTrunc = (int)schema::UI().drawElement("tabs.send", "suggestion-trunc-len").size;
-        std::string dispSug = TruncateAddress(suggestions[si], sugTrunc > 0 ? sugTrunc : 50);
+        std::string dispSug = util::truncateMiddle(suggestions[si], sugTrunc > 0 ? sugTrunc : 50);
         ImGui::PushID((int)si);
         if (ImGui::Selectable(dispSug.c_str())) {
             snprintf(s_to_address, sizeof(s_to_address), "%s", suggestions[si].c_str());
@@ -710,7 +702,7 @@ void RenderSendConfirmPopup(App* app) {
             DrawGlassPanel(popDl, cMin, cMax, gs);
             popDl->AddText(body2, body2->LegacySize,
                 ImVec2(cMin.x + Layout::spacingMd(), cMin.y + Layout::spacingSm()),
-                Success(), TruncateAddress(s_from_address, (size_t)S.drawElement("tabs.send", "confirm-addr-trunc-len").size).c_str());
+                Success(), util::truncateMiddle(s_from_address, (int)S.drawElement("tabs.send", "confirm-addr-trunc-len").size).c_str());
             ImGui::Dummy(ImVec2(popW, addrCardH));
             ImGui::Dummy(ImVec2(0, Layout::spacingSm()));
         }
@@ -724,7 +716,7 @@ void RenderSendConfirmPopup(App* app) {
             DrawGlassPanel(popDl, cMin, cMax, gs);
             popDl->AddText(body2, body2->LegacySize,
                 ImVec2(cMin.x + Layout::spacingMd(), cMin.y + Layout::spacingSm()),
-                Success(), TruncateAddress(s_to_address, (size_t)S.drawElement("tabs.send", "confirm-addr-trunc-len").size).c_str());
+                Success(), util::truncateMiddle(s_to_address, (int)S.drawElement("tabs.send", "confirm-addr-trunc-len").size).c_str());
             ImGui::Dummy(ImVec2(popW, addrCardH));
             ImGui::Dummy(ImVec2(0, Layout::spacingMd()));
         }
@@ -1060,8 +1052,8 @@ static void RenderRecentSends(const WalletState& state, float width, ImFont* cap
 
         // Address (second line)
         float addrX = txX + S.drawElement("tabs.balance", "recent-tx-addr-offset").sizeOr(65.0f);
-        std::string addrDisplay = TruncateAddress(tx.address,
-            (size_t)S.drawElement("tabs.balance", "recent-tx-addr-trunc").sizeOr(20.0f));
+        std::string addrDisplay = util::truncateMiddle(tx.address,
+            (int)S.drawElement("tabs.balance", "recent-tx-addr-trunc").sizeOr(20.0f));
         rowDL->AddText(capFont, capFont->LegacySize,
                        ImVec2(addrX, rowPos.y + 2.0f * dp), OnSurfaceDisabled(), addrDisplay.c_str());