Fix URL reactivity in UploadedFile component

Capture the URL without trailing slash once at component creation to prevent unnecessary reactive updates during navigation.

src/lib/components/chat/UploadedFile.svelte

@@ -20,7 +20,8 @@
 
 	let showModal = $state(false);
 
-	let urlNotTrailing = $derived(page.url.pathname.replace(/\/$/, ""));
+	// Capture URL once at component creation to prevent reactive updates during navigation
+	let urlNotTrailing = page.url.pathname.replace(/\/$/, "");
 
 	function truncateMiddle(text: string, maxLength: number): string {
 		if (text.length <= maxLength) {