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/explorer_tab.cpp

@@ -8,6 +8,8 @@
 #include "../../rpc/rpc_worker.h"
 #include "../../data/wallet_state.h"
 #include "../../util/i18n.h"
+#include "../../util/text_format.h"
+#include "mining_tab_helpers.h"
 #include "../explorer/explorer_block_cache.h"
 #include "../schema/ui_schema.h"
 #include "../material/type.h"
@@ -117,9 +119,7 @@ static const char* relativeTime(int64_t timestamp) {
 }
 
 static std::string truncateHash(const std::string& hash, int front, int back) {
-    if (hash.length() <= static_cast<size_t>(front + back + 3))
-        return hash;
-    return hash.substr(0, front) + "..." + hash.substr(hash.length() - back);
+    return util::truncateMiddle(hash, front, back);
 }
 
 // Adaptive hash truncation based on available pixel width
@@ -176,21 +176,6 @@ static std::string formatSize(int bytes) {
     return b;
 }
 
-static std::string formatHashrate(double hashrate) {
-    char b[32];
-    if (hashrate >= 1e12)
-        snprintf(b, sizeof(b), "%.2f TH/s", hashrate / 1e12);
-    else if (hashrate >= 1e9)
-        snprintf(b, sizeof(b), "%.2f GH/s", hashrate / 1e9);
-    else if (hashrate >= 1e6)
-        snprintf(b, sizeof(b), "%.2f MH/s", hashrate / 1e6);
-    else if (hashrate >= 1e3)
-        snprintf(b, sizeof(b), "%.2f KH/s", hashrate / 1e3);
-    else
-        snprintf(b, sizeof(b), "%.0f H/s", hashrate);
-    return b;
-}
-
 // Copy icon button — draws a small icon that copies text to clipboard on click
 static void copyButton(const char* id, const std::string& text, float x, float y) {
     ImFont* iconFont = Type().iconSmall();
@@ -698,7 +683,7 @@ static void renderChainStats(App* app, float availWidth) {
 
         MetricSpec metrics[4] = {
             { ICON_MD_SPEED, TR("difficulty"), difficulty, "", Warning() },
-            { ICON_MD_SHOW_CHART, TR("peers_hashrate"), formatHashrate(state.mining.networkHashrate), "", Success() },
+            { ICON_MD_SHOW_CHART, TR("peers_hashrate"), FormatHashrate(state.mining.networkHashrate), "", Success() },
             { ICON_MD_CONFIRMATION_NUMBER, TR("peers_notarized"), notarized, "", Primary() },
             { ICON_MD_STORAGE, TR("explorer_mempool"), mempoolTxs, s_mempool_loading ? std::string("") : formatSize(static_cast<int>(s_mempool_size)), Secondary() },
         };
@@ -1030,10 +1015,8 @@ static void renderBlockDetailModal(App* app) {
         // Show a loading modal while fetching
         if (BeginOverlayDialog(TR("loading"), &s_detail_loading, 300.0f, 0.85f)) {
             ImGui::Spacing();
-            int dots = ((int)(ImGui::GetTime() * 3.0f)) % 4;
-            const char* dotStr[] = {"", ".", "..", "..."};
             char loadBuf[64];
-            snprintf(loadBuf, sizeof(loadBuf), "%s%s", TR("loading"), dotStr[dots]);
+            snprintf(loadBuf, sizeof(loadBuf), "%s%s", TR("loading"), material::LoadingDots());
             ImGui::TextDisabled("%s", loadBuf);
             ImGui::Spacing();
             EndOverlayDialog();
@@ -1091,9 +1074,7 @@ static void renderBlockDetailModal(App* app) {
 
     // Show loading state inside the modal when navigating between blocks
     if (s_detail_loading) {
-        int dots = ((int)(ImGui::GetTime() * 3.0f)) % 4;
-        const char* dotStr[] = {"", ".", "..", "..."};
-        snprintf(buf, sizeof(buf), "%s%s", TR("loading"), dotStr[dots]);
+        snprintf(buf, sizeof(buf), "%s%s", TR("loading"), material::LoadingDots());
         ImGui::TextDisabled("%s", buf);
         EndOverlayDialog();
         return;