fix: wrap theme provider in self-invoking function

src/components/ThemeProvider.astro

@@ -2,6 +2,7 @@
 ---
 
 <script is:inline>
+	(function () {
 		const getThemePreference = () => {
 			if (typeof localStorage !== 'undefined' && localStorage.getItem('theme')) {
 				return localStorage.getItem('theme');
@@ -23,4 +24,5 @@
 				attributeFilter: ['class'],
 			});
 		}
+	})();
 </script>