refactor: Modularize JavaScript Code into Separate Files

public/js/utils.js

@@ -0,0 +1,15 @@
+// Shared small utilities
+
+export function showToast(msg) {
+  const el = document.getElementById('toast');
+  if (!el) return;
+  el.textContent = msg;
+  el.style.opacity = '1';
+  setTimeout(() => {
+    el.style.opacity = '0';
+  }, 1200);
+}
+
+export function wire(el, type, handler, options) {
+  if (el) el.addEventListener(type, handler, options);
+}