fix(hidpi): scale security-dialog buttons, market caption, QR inset by dpiScale

HiDPI geometry debt from the audit: 15 security-dialog buttons used a raw 40px
height (undersized vs the scaled label at 1.5x), the market "Updated" caption
used a raw SameLine(0,12), and the QR popup's 28px overlay-inset budget wasn't
scaled (wrapping the address at HiDPI). All now go through ui::Layout::dpiScale().

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

src/ui/windows/market_tab.cpp

@@ -1431,7 +1431,7 @@ static void mktDrawPairSelector(App* app, const std::vector<data::ExchangeInfo>&
         ImGui::Dummy(ImVec2(0, Layout::spacingSm()));
         Type().textColored(TypeStyle::Caption, OnSurfaceDisabled(), TR("market_attribution"));
         if (!market.last_updated.empty()) {
-            ImGui::SameLine(0, 12);
+            ImGui::SameLine(0, 12.0f * Layout::dpiScale());
             snprintf(buf, sizeof(buf), TR("market_updated"), market.last_updated.c_str());
             Type().textColored(TypeStyle::Caption, OnSurfaceDisabled(), buf);
         }