Improve modal overlay UI: add border and semi-transparent background

Enhance the sync modal overlay visibility and aesthetics:
- Add 1px border to content widget using palette(mid) for theme adaptation
- Restore semi-transparent background (alpha=230) to overlay backdrop
- Remove minimum window size constraint (950x550) for better flexibility

The border ensures the overlay is clearly visible in both light and dark
modes, while the semi-transparent background provides visual separation
without completely obscuring the underlying interface

src/qt/forms/modaloverlay.ui

@@ -50,7 +50,7 @@
       <item>
        <widget class="QWidget" name="contentWidget" native="true">
         <property name="styleSheet">
-         <string notr="true">#contentWidget { border-radius: 6px; }
+         <string notr="true">#contentWidget { border: 1px solid palette(mid); border-radius: 6px; }
 QFormLayout QLabel { min-height: 20px; }</string>
         </property>
         <layout class="QVBoxLayout" name="verticalLayoutSub" stretch="1,0,0,0">

src/qt/modaloverlay.cpp

@@ -27,9 +27,11 @@ userClosed(false)
         raise();
     }
 
-    // Set opaque background using palette
+    // Set semi-transparent background
     QPalette pal = ui->bgWidget->palette();
-    pal.setColor(QPalette::Window, pal.color(QPalette::Window));
+    QColor bgColor = pal.color(QPalette::Window);
+    bgColor.setAlpha(230);  // Semi-transparent (0-255, where 255 is opaque)
+    pal.setColor(QPalette::Window, bgColor);
     ui->bgWidget->setAutoFillBackground(true);
     ui->bgWidget->setPalette(pal);
 

src/qt/palladiumgui.cpp

@@ -264,10 +264,6 @@ PalladiumGUI::PalladiumGUI(interfaces::Node& node, const PlatformStyle *_platfor
     // Check beim Start ausführen
     checkUpdate();
     // --- ENDE EINFÜGUNG: UPDATE CHECKER ---
-
-    // Set minimum window size to prevent UI breaking
-    // Must be set AFTER all widgets are configured to ensure it's not overridden
-    setMinimumSize(950, 550);
 }
 
 PalladiumGUI::~PalladiumGUI()