feat(settings): send-tab-style slider for the rescan start height

The optional "scan from block height" control in the Import Private/Viewing
Key dialog now leads with a slider styled like the send-tab amount bar
(rounded track, accent fill, glass thumb) bounded by the chain tip, with the
numeric field beside it for exact entry and the current chain height
right-aligned above. When the node's height is unknown (state_.sync.blocks == 0,
e.g. not yet synced) the slider is omitted and the field spans the full row —
which also fixes the previous cramped 140px field that left the row half empty.

- New static helpers in app.cpp: formatIntWithCommas() and RenderScanHeightControl()
  (mirrors RenderAmountBar in send_tab.cpp). The height decimal string is the single
  source of truth shared by slider + field; the slider reserves/queries its
  InvisibleButton before drawing so a drag has no one-frame lag; the bar height is
  ImGui::GetFrameHeight() so it aligns with the numeric field.
- Import handler clamps the parsed start height to the chain tip.
- i18n: added import_scan_tip ("current height") in en + 8 langs.

Reviewed via an adversarial multi-agent pass (slider-math / state-sync /
dpi-layout / consistency); the one confirmed finding (bar/field height mismatch)
is fixed here.

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

res/lang/de.json

@@ -446,6 +446,7 @@
     "import_private_key": "Privaten Schlüssel importieren...",
     "import_scan_hint": "0 = von Anfang an neu scannen",
     "import_scan_label": "Ab Blockhöhe scannen (optional)",
+    "import_scan_tip": "aktuelle Höhe",
     "import_scan_transparent": "Transparente Schlüssel scannen immer vollständig neu",
     "import_viewkey_field": "Anzeigeschlüssel",
     "import_viewkey_note": "Nur Lesen: Ein Anzeigeschlüssel zeigt Guthaben und Transaktionen einer Adresse, kann deren Mittel aber nicht ausgeben.",

res/lang/es.json

@@ -446,6 +446,7 @@
     "import_private_key": "Importar Clave Privada...",
     "import_scan_hint": "0 = volver a escanear desde el inicio",
     "import_scan_label": "Escanear desde la altura de bloque (opcional)",
+    "import_scan_tip": "altura actual",
     "import_scan_transparent": "Las claves transparentes siempre se reescanean por completo",
     "import_viewkey_field": "Clave de visualización",
     "import_viewkey_note": "Solo lectura: una clave de visualización revela el saldo y las transacciones de una dirección, pero no puede gastar sus fondos.",

res/lang/fr.json

@@ -446,6 +446,7 @@
     "import_private_key": "Importer une clé privée...",
     "import_scan_hint": "0 = réanalyser depuis le début",
     "import_scan_label": "Analyser à partir de la hauteur de bloc (facultatif)",
+    "import_scan_tip": "hauteur actuelle",
     "import_scan_transparent": "Les clés transparentes réanalysent toujours entièrement",
     "import_viewkey_field": "Clé de visualisation",
     "import_viewkey_note": "Lecture seule : une clé de visualisation révèle le solde et les transactions d'une adresse, mais ne peut pas dépenser ses fonds.",

res/lang/ja.json

@@ -446,6 +446,7 @@
     "import_private_key": "秘密鍵をインポート...",
     "import_scan_hint": "0 = 最初から再スキャン",
     "import_scan_label": "スキャン開始ブロック高（任意）",
+    "import_scan_tip": "現在の高さ",
     "import_scan_transparent": "透明鍵は常に全体を再スキャンします",
     "import_viewkey_field": "閲覧鍵",
     "import_viewkey_note": "監視のみ：閲覧鍵はアドレスの残高と取引を表示できますが、資金を送金することはできません。",

res/lang/ko.json

@@ -446,6 +446,7 @@
     "import_private_key": "개인 키 가져오기...",
     "import_scan_hint": "0 = 처음부터 다시 스캔",
     "import_scan_label": "스캔 시작 블록 높이(선택 사항)",
+    "import_scan_tip": "현재 높이",
     "import_scan_transparent": "투명 키는 항상 전체를 다시 스캔합니다",
     "import_viewkey_field": "조회 키",
     "import_viewkey_note": "읽기 전용: 조회 키는 주소의 잔액과 거래를 보여주지만 자금을 사용할 수는 없습니다.",

res/lang/pt.json

@@ -446,6 +446,7 @@
     "import_private_key": "Importar Chave Privada...",
     "import_scan_hint": "0 = reescanear desde o início",
     "import_scan_label": "Escanear a partir da altura do bloco (opcional)",
+    "import_scan_tip": "altura atual",
     "import_scan_transparent": "Chaves transparentes sempre reescaneiam totalmente",
     "import_viewkey_field": "Chave de visualização",
     "import_viewkey_note": "Somente leitura: uma chave de visualização revela o saldo e as transações de um endereço, mas não pode gastar seus fundos.",

res/lang/ru.json

@@ -446,6 +446,7 @@
     "import_private_key": "Импорт приватного ключа...",
     "import_scan_hint": "0 = повторное сканирование с начала",
     "import_scan_label": "Сканировать с высоты блока (необязательно)",
+    "import_scan_tip": "текущая высота",
     "import_scan_transparent": "Прозрачные ключи всегда пересканируются полностью",
     "import_viewkey_field": "Ключ просмотра",
     "import_viewkey_note": "Только чтение: ключ просмотра показывает баланс и транзакции адреса, но не может тратить его средства.",

res/lang/zh.json

@@ -446,6 +446,7 @@
     "import_private_key": "导入私钥...",
     "import_scan_hint": "0 = 从头重新扫描",
     "import_scan_label": "从区块高度开始扫描（可选）",
+    "import_scan_tip": "当前高度",
     "import_scan_transparent": "透明密钥始终完整重新扫描",
     "import_viewkey_field": "查看密钥",
     "import_viewkey_note": "仅查看：查看密钥可显示地址的余额和交易，但无法花费其资金。",

src/app.cpp

@@ -2753,6 +2753,79 @@ void App::renderLiteUnlockPrompt()
     }
 }
 
+// Group an integer height with thousands separators, e.g. 1234567 -> "1,234,567".
+static std::string formatIntWithCommas(long long v)
+{
+    std::string s = std::to_string(v);
+    for (int pos = (int)s.length() - 3; pos > 0; pos -= 3) s.insert(pos, ",");
+    return s;
+}
+
+// A send-tab-style slider (mirrors RenderAmountBar in send_tab.cpp: rounded track, accent fill, glass
+// thumb) for the optional rescan start height, paired with a numeric field for exact entry. Both share
+// `buf` — the height as a decimal string — so it's the single source of truth. `tipHeight` is the chain
+// tip = the slider's max; when <= 0 (height unknown) the slider is omitted and the field spans the row.
+static void RenderScanHeightControl(char* buf, size_t bufSize, int tipHeight, bool enabled, float dp)
+{
+    namespace m = ui::material;
+    int cur = buf[0] ? std::atoi(buf) : 0;
+    if (cur < 0) cur = 0;
+
+    ImGui::BeginDisabled(!enabled);
+
+    const float inputW = 148.0f * dp;
+    if (tipHeight > 0) {
+        const float gap = ui::Layout::spacingSm();
+        float barW = ImGui::GetContentRegionAvail().x - inputW - gap;
+        const float minBar = 120.0f * dp;
+        if (barW < minBar) barW = minBar;
+        const float barH = ImGui::GetFrameHeight();   // match the numeric field's height so the two align (already dp-scaled)
+        const float barRound = barH * 0.5f;
+        const float thumbR = barH * 0.5f;
+
+        const ImVec2 barMin = ImGui::GetCursorScreenPos();
+        const ImVec2 barMax(barMin.x + barW, barMin.y + barH);
+        ImDrawList* dl = ImGui::GetWindowDrawList();
+
+        // Reserve + interact first so the fill/thumb drawn below reflect the current drag (no lag).
+        ImGui::InvisibleButton("##scanbar", ImVec2(barW, barH));
+        const bool active  = enabled && ImGui::IsItemActive();
+        const bool hovered = ImGui::IsItemHovered();
+        if (active) {
+            const float clickPct = std::clamp((ImGui::GetIO().MousePos.x - barMin.x) / barW, 0.0f, 1.0f);
+            cur = (int)lroundf(clickPct * (float)tipHeight);
+            snprintf(buf, bufSize, "%d", cur);
+        }
+        const float pct = std::clamp((float)cur / (float)tipHeight, 0.0f, 1.0f);
+
+        // Track + accent fill up to the thumb (fill's rounded right edge matches the thumb circle).
+        dl->AddRectFilled(barMin, barMax, IM_COL32(255, 255, 255, enabled ? 26 : 12), barRound);
+        const float usableW = barW - thumbR * 2.0f;
+        const float thumbCenterX = barMin.x + thumbR + usableW * pct;
+        const float fillRight = thumbCenterX + thumbR;
+        if (fillRight > barMin.x + barRound * 2.0f)
+            dl->AddRectFilled(barMin, ImVec2(fillRight, barMax.y),
+                              m::WithAlpha(m::Primary(), enabled ? 150 : 55), barRound);
+
+        // Glass thumb.
+        const float thumbY = barMin.y + barH * 0.5f;
+        dl->AddCircleFilled(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 205 : 90), 24);
+        dl->AddCircle(ImVec2(thumbCenterX, thumbY), thumbR, IM_COL32(255, 255, 255, enabled ? 120 : 50), 24, 1.4f * dp);
+
+        if (hovered && enabled) {
+            ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
+            m::Tooltip("%s / %s (%.0f%%)", formatIntWithCommas(cur).c_str(),
+                       formatIntWithCommas(tipHeight).c_str(), pct * 100.0f);
+        }
+        ImGui::SameLine(0, gap);
+    }
+
+    // Exact numeric entry — fills the remaining row (or the whole row when there's no slider).
+    ImGui::SetNextItemWidth(tipHeight > 0 ? inputW : ImGui::GetContentRegionAvail().x);
+    ImGui::InputText("##importscanheight", buf, bufSize, ImGuiInputTextFlags_CharsDecimal);
+
+    ImGui::EndDisabled();
+}
 
 void App::renderImportKeyDialog()
 {
@@ -2863,19 +2936,31 @@ void App::renderImportKeyDialog()
     ImGui::Spacing();
 
     // Optional scan-from height. z_importkey / z_importviewingkey accept a start block, so a shielded
-    // import of a recent key needn't rescan the whole chain. Transparent WIF (importprivkey) has no
+    // import of a recent key needn't rescan the whole chain. A send-tab-style slider (bounded by the
-    // start-height parameter, so the field is disabled + noted once a transparent key is recognized.
+    // chain tip) plus a numeric field set it. Transparent WIF (importprivkey) has no start-height
+    // parameter, so the control is disabled + noted once a transparent key is recognized.
     {
         const bool transparentKey = !viewMode && isSpend && !shielded;   // recognized transparent WIF
         if (transparentKey && import_key_scan_height_[0])
-            sodium_memzero(import_key_scan_height_, sizeof(import_key_scan_height_));  // no stale height in the disabled box
+            sodium_memzero(import_key_scan_height_, sizeof(import_key_scan_height_));  // no stale height
+        const int tip = state_.sync.blocks;   // chain tip = slider max; 0 when unknown
+
+        // Label, with the current chain height right-aligned when known.
+        const float rowStartX = ImGui::GetCursorPosX();
+        const float rowW = ImGui::GetContentRegionAvail().x;
         ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceMedium()), "%s", TR("import_scan_label"));
-        ImGui::BeginDisabled(transparentKey);
+        if (tip > 0) {
-        ImGui::SetNextItemWidth(140.0f * dp);
+            char tipBuf[64];
-        ImGui::InputText("##importscanheight", import_key_scan_height_, sizeof(import_key_scan_height_),
+            snprintf(tipBuf, sizeof(tipBuf), "%s %s", TR("import_scan_tip"), formatIntWithCommas(tip).c_str());
-                         ImGuiInputTextFlags_CharsDecimal);
+            const float targetX = rowStartX + rowW - ImGui::CalcTextSize(tipBuf).x;
-        ImGui::EndDisabled();
+            ImGui::SameLine();
-        ImGui::SameLine(0, ui::Layout::spacingSm());
+            if (targetX > ImGui::GetCursorPosX()) ImGui::SetCursorPosX(targetX);
+            ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceDisabled()), "%s", tipBuf);
+        }
+
+        RenderScanHeightControl(import_key_scan_height_, sizeof(import_key_scan_height_),
+                                tip, !transparentKey, dp);
+
         ImGui::TextColored(ImGui::ColorConvertU32ToFloat4(m::OnSurfaceDisabled()), "%s",
                            transparentKey ? TR("import_scan_transparent") : TR("import_scan_hint"));
         ImGui::Spacing();
@@ -2918,6 +3003,8 @@ void App::renderImportKeyDialog()
         if (import_key_scan_height_[0]) {   // it; importPrivateKey ignores it for transparent WIF.
             startHeight = std::atoi(import_key_scan_height_);
             if (startHeight < 0) startHeight = 0;
+            if (state_.sync.blocks > 0 && startHeight > state_.sync.blocks)
+                startHeight = state_.sync.blocks;   // never past the chain tip
         }
         importPrivateKey(std::string(import_key_input_), startHeight,
                          [this](bool ok, const std::string& err, const std::string& addr) {

src/util/i18n.cpp

@@ -1369,6 +1369,7 @@ void I18n::loadBuiltinEnglish()
         strings_["import_scan_label"] = "Scan from block height (optional)";
         strings_["import_scan_hint"] = "0 = rescan from the start";
         strings_["import_scan_transparent"] = "Transparent keys always rescan fully";
+        strings_["import_scan_tip"] = "current height";
 
         // --- Key Export Dialog ---
         strings_["key_export_fetching"] = "Fetching key from wallet...";