fix(FOUC): Always register timeout animation

We need the animation to start regardless of the
defined state of custom elements. Otherwise the
animation will not start early enough.

(cherry picked from commit 97210b0)

Author: tvdeyen

app/assets/builds/alchemy/admin.css

@@ -1,5 +1,11 @@
 @use "../mixins";
 
+@property --custom-elements-loaded {
+  syntax: "<number>";
+  inherits: true;
+  initial-value: 0;
+}
+
 html {
   box-sizing: border-box;
   height: 100%;
@@ -49,6 +55,7 @@ body {
   cursor: default;
   opacity: 1;
   transition: opacity var(--transition-duration);
+  animation: custom-elements-loaded 0 linear 250ms forwards;
 
   // Fix for strange element window offset
   &.pages.edit {
@@ -61,7 +68,6 @@ body {
 
   &:has(:not(:defined)) {
     opacity: var(--custom-elements-loaded, 0);
-    animation: custom-elements-loaded 0 linear 250ms forwards;
   }
 }