Fix desktop app overscrolling inappropriately (#6350)

# Description of Changes
Fix #6348

frontend/src/core/components/shared/AppConfigModal.css

@@ -3,11 +3,11 @@
   display: flex;
   gap: 0;
   height: 45rem; /* 720px */
+  max-height: 90dvh; /* matches Mantine's default modal max-height so the outer wrapper never has to scroll */
 }
 
 .modal-nav {
   width: 15rem; /* 240px */
-  height: 45rem; /* 720px */
   border-top-left-radius: 0.75rem; /* 12px */
   border-bottom-left-radius: 0.75rem; /* 12px */
   overflow: hidden;
@@ -108,7 +108,6 @@
 
 .modal-content {
   flex: 1;
-  height: 45rem; /* 720px */
   display: flex;
   flex-direction: column;
   overflow: hidden;

frontend/src/core/components/shared/AppConfigModal.tsx

@@ -164,6 +164,7 @@ const AppConfigModalInner: React.FC<AppConfigModalProps> = ({
       overlayProps={{ opacity: 0.35, blur: 2 }}
       padding={0}
       fullScreen={isMobile}
+      styles={{ content: { overflowY: "hidden", overscrollBehavior: "none" } }}
     >
       <div className="modal-container">
         {/* Left navigation */}

frontend/src/core/styles/index.css

@@ -3,7 +3,8 @@ body {
   margin: 0;
   padding: 0;
   height: 100%;
-  overflow-x: hidden;
+  overflow: hidden;
+  overscroll-behavior: none;
 }
 
 body {