fix(frontend): MkModalのスクロールを復活させる

packages/frontend/src/components/MkModal.vue

@@ -431,9 +431,15 @@ defineExpose({
 			margin: auto;
 			padding: 32px;
 			display: flex;
+			// TODO: mask-imageはiOSだとやたら重い。なんとかしたい
+			-webkit-mask-image: linear-gradient(0deg, rgba(0,0,0,0) 0%, rgba(0,0,0,1) 32px, rgba(0,0,0,1) calc(100% - 32px), rgba(0,0,0,0) 100%);
+			mask-image: linear-gradient(0deg, rgba(0,0,0,0) 0%, rgba(0,0,0,1) 32px, rgba(0,0,0,1) calc(100% - 32px), rgba(0,0,0,0) 100%);
+			overflow: auto;
 
 			@media (max-width: 500px) {
 				padding: 16px;
+				-webkit-mask-image: linear-gradient(0deg, rgba(0,0,0,0) 0%, rgba(0,0,0,1) 16px, rgba(0,0,0,1) calc(100% - 16px), rgba(0,0,0,0) 100%);
+				mask-image: linear-gradient(0deg, rgba(0,0,0,0) 0%, rgba(0,0,0,1) 16px, rgba(0,0,0,1) calc(100% - 16px), rgba(0,0,0,0) 100%);
 			}
 		}
 	}