fix(clipboard): add fallback helper and unify copy actions

src/utils/clipboard.ts

@@ -0,0 +1,49 @@
+export async function copyToClipboard(text: string): Promise<boolean> {
+  try {
+    if (typeof navigator !== 'undefined' && navigator.clipboard?.writeText) {
+      await navigator.clipboard.writeText(text);
+      return true;
+    }
+  } catch {
+    // fallback below
+  }
+
+  try {
+    if (typeof document === 'undefined') return false;
+    if (!document.body) return false;
+
+    const activeElement = document.activeElement as HTMLElement | null;
+
+    const textarea = document.createElement('textarea');
+    textarea.value = text;
+    textarea.setAttribute('readonly', '');
+    textarea.style.position = 'fixed';
+    textarea.style.opacity = '0';
+    textarea.style.pointerEvents = 'none';
+    textarea.style.left = '-9999px';
+    textarea.style.top = '0';
+    textarea.style.width = '1px';
+    textarea.style.height = '1px';
+    textarea.style.padding = '0';
+    textarea.style.border = '0';
+
+    document.body.appendChild(textarea);
+    textarea.focus();
+    textarea.select();
+    textarea.setSelectionRange(0, textarea.value.length);
+    const copied = document.execCommand('copy');
+    document.body.removeChild(textarea);
+
+    if (activeElement?.focus) {
+      try {
+        activeElement.focus();
+      } catch {
+        // ignore
+      }
+    }
+
+    return copied;
+  } catch {
+    return false;
+  }
+}