opt: add scale animation to overlay content, fix text alignment issue in add system app overlay

module/webui/styles/global.css

@@ -42,12 +42,22 @@ body {
     width: 100vw;
     height: 100vh;
     background-color: rgba(0, 0, 0, 0.5);
+    backdrop-filter: blur(5px);
     display: none;
     justify-content: center;
     opacity: 0;
     transition: opacity 0.2s ease;
 }
 
+.overlay-content {
+    transform: scale(0.8);
+    transition: transform 0.2s ease;
+}
+
+.overlay-content.open {
+    transform: scale(1);
+}
+
 .close-btn {
     position: absolute;
     top: 12px;

module/webui/styles/system_app.css

@@ -11,7 +11,7 @@
     width: calc(90vw - 60px);
     max-width: 400px;
     max-height: calc(80vh - 60px);
-    overflow-y: scroll;
+    overflow-y: auto;
     padding: 30px;
     background-color: #fff;
     border-radius: 15px;
@@ -19,6 +19,7 @@
 }
 
 .add-system-app-title {
+    text-align: center;
     font-size: 26px;
     user-select: none;
     margin-bottom: 20px;
@@ -57,6 +58,7 @@
 }
 
 .current-system-app-list {
+    text-align: center;
     margin-top: 25px;
     margin-bottom: 10px;
     user-select: none;