fix: stagger animation breaking position:fixed overlays

The fadeSlideIn animation used transform:translateY which creates a
new containing block, trapping position:fixed children (EntitySelect).
Switched to the CSS translate property which doesn't create a
containing block.

frontend/src/app.css

@@ -132,8 +132,8 @@ a:focus-visible {
 
 /* Animations */
 @keyframes fadeSlideIn {
-	from { opacity: 0; transform: translateY(12px); }
-	to { opacity: 1; transform: translateY(0); }
+	from { opacity: 0; translate: 0 12px; }
+	to { opacity: 1; translate: none; }
 }
 
 @keyframes shimmer {