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/transactions_tab.cpp

@@ -37,13 +37,6 @@ static std::string TrId(const char* key, const char* id) {
     return std::string(TR(key)) + "##" + id;
 }
 
-// Helper to truncate strings
-static std::string truncateString(const std::string& str, int maxLen = 16) {
-    if (str.length() <= static_cast<size_t>(maxLen)) return str;
-    int half = (maxLen - 3) / 2;
-    return str.substr(0, half) + "..." + str.substr(str.length() - half);
-}
-
 // Case-insensitive string search
 static bool containsIgnoreCase(const std::string& str, const std::string& search) {
     return dragonx::util::containsIgnoreCase(str, search);
@@ -358,9 +351,7 @@ void RenderTransactionsTab(App* app)
             ImGui::TextColored(ImVec4(0.6f, 0.8f, 1.0f, pulse), ICON_MD_HOURGLASS_EMPTY);
             ImGui::PopFont();
             ImGui::SameLine(0, Layout::spacingXs());
-            int dots = ((int)(ImGui::GetTime() * 3.0f)) % 4;
-            const char* dotStr[] = {"", ".", "..", "..."};
-            ImGui::TextColored(ImVec4(0.6f, 0.8f, 1.0f, 1.0f), "%s%s", txLoadingText.c_str(), dotStr[dots]);
+            ImGui::TextColored(ImVec4(0.6f, 0.8f, 1.0f, 1.0f), "%s%s", txLoadingText.c_str(), material::LoadingDots());
         }
 
         ImGui::Dummy(ImVec2(0, Layout::spacingSm() + Layout::spacingXs()));
@@ -679,9 +670,7 @@ void RenderTransactionsTab(App* app)
             } else if (state.transactions.empty()) {
                 ImGui::Dummy(ImVec2(0, 20));
                 if (txLoading) {
-                    int dots = ((int)(ImGui::GetTime() * 3.0f)) % 4;
-                    const char* dotStr[] = {"", ".", "..", "..."};
-                    snprintf(buf, sizeof(buf), "%s%s", txLoadingText.c_str(), dotStr[dots]);
+                    snprintf(buf, sizeof(buf), "%s%s", txLoadingText.c_str(), material::LoadingDots());
                     Type().textColored(TypeStyle::Caption, OnSurfaceDisabled(), buf);
                 } else {
                     Type().textColored(TypeStyle::Caption, OnSurfaceDisabled(), TR("no_transactions"));
@@ -756,7 +745,7 @@ void RenderTransactionsTab(App* app)
                                 OnSurfaceDisabled(), ago.c_str());
 
                     // Address (second line, left side)
-                    std::string addr_display = truncateString(tx.address, (addrLabel.truncate > 0) ? addrLabel.truncate : 20);
+                    std::string addr_display = util::truncateMiddle(tx.address, (addrLabel.truncate > 0) ? addrLabel.truncate : 20);
                     dl->AddText(capFont, capFont->LegacySize, ImVec2(labelX, cy + body2->LegacySize + Layout::spacingXs()),
                                 OnSurfaceMedium(), addr_display.c_str());