fix(frontend): center loading spinner on large screens by using full-viewport container and removing #root max-width constraint

packages/frontend/src/App.css

@@ -12,8 +12,9 @@ html, body, #root {
   overflow: hidden;
 }
 
+/* Ensure full-viewport centering for loading state */
 #root {
-  max-width: 1280px;
+  max-width: none;
 }
 
 .logo {

packages/frontend/src/App.tsx

@@ -405,7 +405,7 @@ const RekordboxReader: React.FC = () => {
 
   if (xmlLoading) {
     return (
-      <Flex height="100vh" align="center" justify="center" direction="column" gap={4}>
+      <Flex height="100vh" width="100vw" align="center" justify="center" direction="column" gap={4}>
         <Spinner size="xl" />
         <Text>Loading your library...</Text>
       </Flex>