fix(ui): make HiDPI-overflowing containers scrollable — wizard, overlay dialogs, balance recent-tx

At font_scale 1.5 (dpiScale 1.5) three fixed, non-scrolling containers clipped
content off the bottom with no scroll escape:

- First-run wizard: the hand-drawn cards grow ~1.5x past the fixed window,
  pushing Continue / Encrypt & Continue / Skip off-screen (a setup blocker).
  Inject a wheel-driven scroll offset into the layout seed + a scroll indicator;
  gate the wheel on !IsPopupOpen + NoPopupHierarchy so an open combo popup does
  not scroll the wizard behind it. No-op at 1.0x.
- Overlay dialogs (BeginOverlayDialog): auto-height cards taller than the
  viewport (About, Request Payment) ran their footer off the bottom. Add a
  sticky per-open overflow flag that clamps the card to the viewport and makes
  the content child scrollable; short dialogs still center unchanged. Give the
  nested settings clear-history confirm its own idSuffix so it can't inherit the
  parent dialog's overflow state or collide on the child window id.
- Balance Recent Transactions: the dp-scaled address card evicted the recent-tx
  list off the non-scrolling tab host. Cap the card inside RenderSharedAddressList
  against the space that actually remains (minus a caller-provided reserve) so
  the section below stays on-screen — covers all 10 balance layouts.

Verified at font_scale 1.5 across full-node + Lite + Windows (ctest green) and an
adversarial diff review (two low-severity regressions found + fixed).

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

src/app_wizard.cpp

@@ -177,8 +177,28 @@ void App::renderFirstRunWizard() {
     // DPI scale factor — multiply all pixel constants by dp
     const float dp = ui::Layout::dpiScale();
 
+    // Vertical scroll: the wizard cards are hand-drawn at absolute Y offsets and grow ~1.5x with the
+    // font-scale setting, so at high scale the focused card's primary button (Continue / Encrypt & Continue
+    // / Skip) can fall below the fixed window. Offset the whole layout by a wheel-driven scroll, clamped to
+    // last frame's measured content height, so every control stays reachable. The window keeps
+    // NoScrollWithMouse, so ImGui doesn't consume the wheel — we read the raw delta and apply our own offset.
+    static float s_wizScroll = 0.0f, s_wizContentH = 0.0f;
+    if (ImGui::IsWindowAppearing()) s_wizScroll = 0.0f;
+    const float wizMaxScroll = std::max(0.0f, s_wizContentH - winSize.y);
+    // Don't steal the wheel from an open combo popup (e.g. the 9-item Language dropdown, which is a
+    // scrollable popup): NoPopupHierarchy stops the popup counting as hovering the wizard, and the
+    // IsPopupOpen guard ensures no wheel is consumed for the whole wizard while any popup is showing.
+    const bool wizPopupOpen = ImGui::IsPopupOpen("", ImGuiPopupFlags_AnyPopupId | ImGuiPopupFlags_AnyPopupLevel);
+    if (wizMaxScroll > 0.0f && !wizPopupOpen &&
+        ImGui::IsWindowHovered(ImGuiHoveredFlags_ChildWindows | ImGuiHoveredFlags_NoPopupHierarchy)) {
+        float wheel = ImGui::GetIO().MouseWheel;
+        if (wheel != 0.0f) s_wizScroll -= wheel * 60.0f * dp;
+    }
+    s_wizScroll = std::max(0.0f, std::min(s_wizScroll, wizMaxScroll));
+    const float scrollY = s_wizScroll;
+
     // --- Header: Logo + Welcome ---
-    float headerCy = winPos.y + 20.0f * dp;
+    float headerCy = winPos.y - scrollY + 20.0f * dp;
     float logoSize = S.drawElement("screens.first-run", "logo").sizeOr(56.0f);
     if (logo_tex_ != 0) {
         float aspect = (logo_h_ > 0) ? (float)logo_w_ / (float)logo_h_ : 1.0f;
@@ -1428,6 +1448,21 @@ void App::renderFirstRunWizard() {
     // Merge channels: backgrounds → content → overlays
     dl->ChannelsMerge();
 
+    // Measure this frame's content height (feeds next frame's scroll clamp) and, when it overflows the
+    // window, draw a slim scroll indicator so the off-screen content is discoverable.
+    {
+        float contentBottom = std::max(card0Bot, std::max(card1Bot, card2Bot));
+        s_wizContentH = (contentBottom - winPos.y + scrollY) + 24.0f * dp;
+        if (wizMaxScroll > 0.0f && s_wizContentH > 0.0f) {
+            float trackH = winSize.y - 8.0f * dp;
+            float thumbH = std::min(trackH, std::max(32.0f * dp, trackH * (winSize.y / s_wizContentH)));
+            float thumbY = winPos.y + 4.0f * dp + (trackH - thumbH) * (scrollY / wizMaxScroll);
+            float barX   = winPos.x + winSize.x - 6.0f * dp;
+            dl->AddRectFilled(ImVec2(barX, thumbY), ImVec2(barX + 3.0f * dp, thumbY + thumbH),
+                              ui::material::WithAlpha(ui::material::OnSurface(), 55), 1.5f * dp);
+        }
+    }
+
     ImGui::End();
 }