fix: Reset PDF state on dialog open

Author: allozaur

tools/server/webui/src/lib/components/app/chat/ChatAttachments/ChatAttachmentPreviewDialog.svelte

@@ -134,6 +134,15 @@
 		}
 	}
 
+	$effect(() => {
+		if (open) {
+			pdfImages = [];
+			pdfImagesLoading = false;
+			pdfImagesError = null;
+			pdfViewMode = 'pages';
+		}
+	});
+
 	$effect(() => {
 		if (open && isPdf && pdfViewMode === 'pages') {
 			loadPdfImages();