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/balance_tab.cpp

@@ -733,10 +733,8 @@ static void RenderBalanceClassic(App* app)
         bool addrSyncing = state.sync.syncing && !state.sync.isSynced();
         ImGui::BeginDisabled(addrSyncing);
         if (s_generating_z_address) {
-            int dots = ((int)(ImGui::GetTime() * 3.0f)) % 4;
-            const char* dotStr[] = {"", ".", "..", "..."};
             char genLabel[64];
-            snprintf(genLabel, sizeof(genLabel), "%s%s##bal_z", TR("generating"), dotStr[dots]);
+            snprintf(genLabel, sizeof(genLabel), "%s%s##bal_z", TR("generating"), material::LoadingDots());
             TactileButton(genLabel, ImVec2(buttonWidth, 0), S.resolveFont(addrBtn.font.empty() ? "button" : addrBtn.font));
         } else if (TactileButton(TR("new_z_address"), ImVec2(buttonWidth, 0), S.resolveFont(addrBtn.font.empty() ? "button" : addrBtn.font))) {
             s_generating_z_address = true;
@@ -2189,9 +2187,9 @@ static void RenderBalanceShield(App* app) {
         // Label below gauge
         ImFont* capFont = Type().caption();
         const char* statusMsg;
-        if (privPct >= 80.0f) statusMsg = "Great privacy!";
-        else if (privPct >= 50.0f) statusMsg = "Consider shielding more";
-        else statusMsg = "Low privacy — shield funds";
+        if (privPct >= 80.0f) statusMsg = TR("privacy_great");
+        else if (privPct >= 50.0f) statusMsg = TR("privacy_medium");
+        else statusMsg = TR("privacy_low");
         ImVec2 msgSz = capFont->CalcTextSizeA(capFont->LegacySize, 1000, 0, statusMsg);
         dl->AddText(capFont, capFont->LegacySize,
                     ImVec2(gaugeCx - msgSz.x * 0.5f, gaugeCy + 4 * dp),
@@ -2307,7 +2305,7 @@ static void RenderBalanceTimeline(App* app) {
         DrawGlassPanel(dl, chartMin, chartMax, spec);
 
         ImFont* capFont = Type().caption();
-        const char* msg = "Balance history — collecting data...";
+        const char* msg = TR("balance_history_collecting");
         ImVec2 msgSz = capFont->CalcTextSizeA(capFont->LegacySize, 10000, 0, msg);
         dl->AddText(capFont, capFont->LegacySize,
                     ImVec2(chartMin.x + (availW - msgSz.x) * 0.5f,
@@ -2629,10 +2627,10 @@ static void RenderBalanceMinimal(App* app) {
     ImGui::Dummy(heroSz);
 
     // Line 2: Shielded + Transparent
-    snprintf(buf, sizeof(buf), "Shielded: %.8f", s_dispShielded);
+    snprintf(buf, sizeof(buf), TR("balance_shielded_fmt"), s_dispShielded);
     Type().textColored(TypeStyle::Caption, Success(), buf);
     ImGui::SameLine(0, Layout::spacingLg());
-    snprintf(buf, sizeof(buf), "Transparent: %.8f", s_dispTransparent);
+    snprintf(buf, sizeof(buf), TR("balance_transparent_fmt"), s_dispTransparent);
     Type().textColored(TypeStyle::Caption, Warning(), buf);
 
     // USD value