fix: remove all transform from stagger/fade animations

Any transform (even transform:none) in animation keyframes with
fill-mode creates a containing block that traps position:fixed
overlays. Removed transform entirely — fade-in only with opacity.

frontend/src/app.css

@@ -132,8 +132,8 @@ a:focus-visible {
 
 /* Animations */
 @keyframes fadeSlideIn {
-	from { opacity: 0; translate: 0 12px; }
-	to { opacity: 1; translate: none; }
+	from { opacity: 0; }
+	to { opacity: 1; }
 }
 
 @keyframes shimmer {
@@ -147,12 +147,12 @@ a:focus-visible {
 }
 
 @keyframes countUp {
-	from { opacity: 0; transform: translateY(8px); }
-	to { opacity: 1; transform: translateY(0); }
+	from { opacity: 0; }
+	to { opacity: 1; }
 }
 
 .animate-fade-slide-in {
-	animation: fadeSlideIn 0.4s ease-out both;
+	animation: fadeSlideIn 0.4s ease-out forwards;
 }
 
 .animate-shimmer {
@@ -171,7 +171,7 @@ a:focus-visible {
 
 /* Stagger children utility */
 .stagger-children > * {
-	animation: fadeSlideIn 0.4s ease-out both;
+	animation: fadeSlideIn 0.4s ease-out forwards;
 }
 .stagger-children > *:nth-child(1) { animation-delay: 0ms; }
 .stagger-children > *:nth-child(2) { animation-delay: 60ms; }