refactor(LoadingFallback): enhance layout stability and styling for loading state

Author: balazs-szucs

frontend/src/core/components/shared/LoadingFallback.tsx

@@ -1,19 +1,25 @@
 /**
- * Loading fallback component for i18next suspense
+ * Loading fallback component for i18next suspense and lazy components.
+ * Uses 100% height to fill its parent container without causing layout shifts
+ * by forcing a 100vh height in contained areas.
  */
 export function LoadingFallback() {
   return (
     <div
       style={{
         display: "flex",
+        flexDirection: "column",
         justifyContent: "center",
         alignItems: "center",
-        height: "100vh",
+        height: "100%",
+        width: "100%",
+        minHeight: "200px",
         fontSize: "18px",
-        color: "#666",
+        color: "var(--text-muted, #666)",
+        background: "transparent",
       }}
     >
-      Loading...
+      <div className="animate-pulse">Loading...</div>
     </div>
   );
 }