perf(webview-ui): add LRU cache to escapeHtml function

- Add LRU cache with 500 item limit for escapeHtml results
- Improves performance by caching frequently escaped strings
- Reduces redundant HTML escaping operations

Author: daniel-lxs

webview-ui/src/utils/highlight.ts

@@ -1,10 +1,27 @@
+import { LRUCache } from "lru-cache"
+
+// LRU cache for escapeHtml with reasonable size limit
+const escapeHtmlCache = new LRUCache<string, string>({ max: 500 })
+
 function escapeHtml(text: string): string {
-	return text
+	// Check cache first
+	const cached = escapeHtmlCache.get(text)
+	if (cached !== undefined) {
+		return cached
+	}
+
+	// Compute escaped text
+	const escaped = text
 		.replace(/&/g, "&amp;")
 		.replace(/</g, "&lt;")
 		.replace(/>/g, "&gt;")
 		.replace(/"/g, "&quot;")
 		.replace(/'/g, "&#39;")
+
+	// Cache the result
+	escapeHtmlCache.set(text, escaped)
+
+	return escaped
 }
 
 export function highlightFzfMatch(