refactor: change background image css style

css/style.css

@@ -1,4 +1,9 @@
-.gradio-container {background: url('file=medias/bg_clear.png')}
+.gradio-container {
+    background: url('file=media/bg_clear.png'), linear-gradient(180deg, rgba(255,255,255,1) 0%, rgba(255,255,255,1) 50%, rgba(255,255,255,0) 100%);
+    background-size: cover;
+    background-position: center center;
+    background-repeat: no-repeat;
+}
 
 #user_avatar {
     background-color: transparent !important;