Optimize frontend rendering, CSS, and backend history caching

server.mjs

@@ -82,17 +82,22 @@ console.log(`[startup] Listening on:  http://0.0.0.0:${PORT}`);
 // History helpers
 // ──────────────────────────────────────────────────────────────────────────────
 
+let historyCache = null;
+
 async function readHistory() {
+  if (historyCache !== null) return historyCache;
   try {
     const raw = await readFile(HISTORY_FILE, 'utf-8');
     const parsed = JSON.parse(raw);
-    return Array.isArray(parsed) ? parsed : [];
+    historyCache = Array.isArray(parsed) ? parsed : [];
   } catch {
-    return [];
+    historyCache = [];
   }
+  return historyCache;
 }
 
 async function writeHistory(entries) {
+  historyCache = entries;
   await writeFile(HISTORY_FILE, JSON.stringify(entries, null, 2), 'utf-8');
 }