use exact hard-coded gradient on header and card placeholders

public/assets/css/main.css

@@ -116,12 +116,10 @@
   border-radius: 7px 7px 0 0;
   background: linear-gradient(
     180deg,
-    var(--gradient-start) 0%,
-    var(--gradient-2) 20%,
-    var(--gradient-3) 40%,
-    var(--gradient-4) 60%,
-    var(--gradient-4) 88%,
-    var(--header-gradient-fade) 96%
+    rgba(60, 133, 108, 1) 0%,
+    rgba(96, 236, 180, 1) 33%,
+    rgba(227, 144, 255, 1) 66%,
+    rgba(149, 87, 181, 1) 100%
   );
 }