feat: add external link confirmation dialog for product URLs

Show an external link icon on ItemCard and CandidateCard that opens a
confirmation dialog before navigating to product URLs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/client/components/CandidateCard.tsx

@@ -10,6 +10,7 @@ interface CandidateCardProps {
 	categoryName: string;
 	categoryIcon: string;
 	imageFilename: string | null;
+	productUrl?: string | null;
 	threadId: number;
 	isActive: boolean;
 }
@@ -22,6 +23,7 @@ export function CandidateCard({
 	categoryName,
 	categoryIcon,
 	imageFilename,
+	productUrl,
 	threadId,
 	isActive,
 }: CandidateCardProps) {
@@ -30,9 +32,38 @@ export function CandidateCard({
 		(s) => s.openConfirmDeleteCandidate,
 	);
 	const openResolveDialog = useUIStore((s) => s.openResolveDialog);
+	const openExternalLink = useUIStore((s) => s.openExternalLink);
 
 	return (
-		<div className="bg-white rounded-xl border border-gray-100 hover:border-gray-200 hover:shadow-sm transition-all overflow-hidden">
+		<div className="relative bg-white rounded-xl border border-gray-100 hover:border-gray-200 hover:shadow-sm transition-all overflow-hidden group">
+			{productUrl && (
+				<span
+					role="button"
+					tabIndex={0}
+					onClick={() => openExternalLink(productUrl)}
+					onKeyDown={(e) => {
+						if (e.key === "Enter" || e.key === " ") {
+							openExternalLink(productUrl);
+						}
+					}}
+					className="absolute top-2 right-2 z-10 w-6 h-6 flex items-center justify-center rounded-full bg-gray-100/80 text-gray-400 hover:bg-blue-100 hover:text-blue-500 opacity-0 group-hover:opacity-100 transition-all cursor-pointer"
+					title="Open product link"
+				>
+					<svg
+						className="w-3.5 h-3.5"
+						fill="none"
+						stroke="currentColor"
+						viewBox="0 0 24 24"
+					>
+						<path
+							strokeLinecap="round"
+							strokeLinejoin="round"
+							strokeWidth={2}
+							d="M18 13v6a2 2 0 01-2 2H5a2 2 0 01-2-2V8a2 2 0 012-2h6M15 3h6v6M10 14L21 3"
+						/>
+					</svg>
+				</span>
+			)}
 			<div className="aspect-[4/3] bg-gray-50">
 				{imageFilename ? (
 					<img