feat(keys): improve the key-export modal — auto-clear copy, inline QR, cleaner actions

- Auto-clear: the Copy button now routes through App::copySecretToClipboard, so a copied
  private/viewing key is wiped from the clipboard after ~45s (same protection as the seed) with
  a "auto-clears" notice — instead of the raw SetClipboardText that left it indefinitely.
- QR: once the key is revealed, a Show/Hide QR toggle renders the key's QR inline (via the same
  GenerateQRTexture/RenderQRCode widget the Receive tab uses) for scanning into another wallet.
  The QR texture is cached, regenerated on key change, and freed on hide/close/dismiss; hiding the
  key also hides its QR.
- Actions row tightened to Show/Hide · Copy · QR, and the key + QR texture are now cleared on any
  dismissal (Close button, scrim click, Esc), not just the Close button.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/key_export_dialog.cpp

@@ -9,6 +9,9 @@
 #include "../../util/i18n.h"
 #include "../schema/ui_schema.h"
 #include "../material/draw_helpers.h"
+#include "../material/type.h"
+#include "../material/colors.h"
+#include "../widgets/qr_code.h"
 #include "imgui.h"
 
 namespace dragonx {
@@ -18,16 +21,27 @@ namespace ui {
 bool KeyExportDialog::s_open = false;
 bool KeyExportDialog::s_fetching = false;
 bool KeyExportDialog::s_show_key = false;
+bool KeyExportDialog::s_show_qr = false;
+std::uintptr_t KeyExportDialog::s_qr_tex = 0;
+std::string KeyExportDialog::s_qr_cached;
 KeyExportDialog::KeyType KeyExportDialog::s_key_type = KeyExportDialog::KeyType::Private;
 std::string KeyExportDialog::s_address;
 std::string KeyExportDialog::s_key;
 std::string KeyExportDialog::s_error;
 
+void KeyExportDialog::releaseQr()
+{
+    if (s_qr_tex) { FreeQRTexture(s_qr_tex); s_qr_tex = 0; }
+    s_qr_cached.clear();
+    s_show_qr = false;
+}
+
 void KeyExportDialog::show(const std::string& address, KeyType type)
 {
     s_open = true;
     s_fetching = false;
     s_show_key = false;
+    releaseQr();
     s_key_type = type;
     s_address = address;
     s_key.clear();
@@ -198,18 +212,43 @@ void KeyExportDialog::render(App* app)
                                            ImVec2(-1, keyDisplay.height > 0 ? keyDisplay.height : 80), ImGuiInputTextFlags_ReadOnly);
             }
 
-            // Show/Hide and Copy buttons
+            // Action row: Show/Hide · Copy · QR
             ImGui::Spacing();
 
             if (material::StyledButton(s_show_key ? TR("hide") : TR("show"), ImVec2(toggleBtn.width, 0), S.resolveFont(toggleBtn.font))) {
                 s_show_key = !s_show_key;
+                if (!s_show_key) s_show_qr = false;  // hiding the key also hides its QR
             }
 
             ImGui::SameLine();
 
             if (material::StyledButton(TR("copy_to_clipboard"), ImVec2(copyBtn.width, 0), S.resolveFont(copyBtn.font))) {
-                ImGui::SetClipboardText(s_key.c_str());
+                // Auto-clearing clipboard: the key (as sensitive as the seed) is wiped after ~45s.
-                // Could add a notification here
+                app->copySecretToClipboard(s_key);
+            }
+
+            // QR (only once revealed) — for scanning the key into another wallet.
+            if (s_show_key) {
+                ImGui::SameLine();
+                if (material::StyledButton(s_show_qr ? TR("hide_qr") : TR("show_qr"),
+                                           ImVec2(copyBtn.width, 0), S.resolveFont(copyBtn.font))) {
+                    s_show_qr = !s_show_qr;
+                }
+            }
+
+            if (s_show_qr && s_show_key && !s_key.empty()) {
+                if (s_qr_cached != s_key) {  // (re)generate the QR texture when the key changes
+                    if (s_qr_tex) { FreeQRTexture(s_qr_tex); s_qr_tex = 0; }
+                    int qw = 0, qh = 0;
+                    s_qr_tex = GenerateQRTexture(s_key.c_str(), &qw, &qh);
+                    s_qr_cached = s_key;
+                }
+                if (s_qr_tex) {
+                    ImGui::Spacing();
+                    const float qrSize = 180.0f;
+                    ImGui::SetCursorPosX((ImGui::GetWindowWidth() - qrSize) * 0.5f);
+                    RenderQRCode(s_qr_tex, qrSize);
+                }
             }
         }
 
@@ -227,10 +266,18 @@ void KeyExportDialog::render(App* app)
             // Clear sensitive data
             s_key.clear();
             s_show_key = false;
+            releaseQr();
         }
 
         material::EndOverlayDialog();
     }
+
+    // Dialog dismissed any other way (scrim click / Esc): drop the key + its QR texture.
+    if (!s_open) {
+        if (!s_key.empty()) s_key.clear();
+        s_show_key = false;
+        releaseQr();
+    }
 }
 
 } // namespace ui

src/ui/windows/key_export_dialog.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <cstdint>
 #include <string>
 
 namespace dragonx {
@@ -47,10 +48,15 @@ private:
     static bool s_open;
     static bool s_fetching;
     static bool s_show_key;
+    static bool s_show_qr;            // inline QR of the revealed key (for scanning into another wallet)
+    static std::uintptr_t s_qr_tex;  // cached QR texture handle (0 = none)
+    static std::string s_qr_cached;  // key the cached QR was generated for
     static KeyType s_key_type;
     static std::string s_address;
     static std::string s_key;
     static std::string s_error;
+
+    static void releaseQr();  // free the QR texture + reset its state
 };
 
 } // namespace ui

src/util/i18n.cpp

@@ -673,6 +673,8 @@ void I18n::loadBuiltinEnglish()
         strings_["address_details"] = "Address Details";
         strings_["view_on_explorer"] = "View on Explorer";
         strings_["qr_code"] = "QR Code";
+        strings_["show_qr"] = "Show QR";
+        strings_["hide_qr"] = "Hide QR";
         strings_["request_payment"] = "Request Payment";
         
         // Transactions Tab