rebase www template

frontend/app/shared.js

@@ -0,0 +1,21 @@
+export const API = '/api';
+
+export function setupCopyBtn(btn, getText) {
+  if (!btn) return;
+  btn.addEventListener('click', () => {
+    const text = getText();
+    if (!text) return;
+    navigator.clipboard.writeText(text).then(() => {
+      const orig = btn.textContent;
+      btn.textContent = '✓ copied';
+      btn.classList.add('copied');
+      setTimeout(() => { btn.textContent = orig; btn.classList.remove('copied'); }, 1500);
+    }).catch(() => {});
+  });
+}
+
+export function showError(el, msg) {
+  if (!el) return;
+  el.textContent = msg ? `Error: ${msg}` : '';
+  el.classList.toggle('hidden', !msg);
+}