feat(FN-4951): complete Step 1 — add shared clipboard utility

Fusion-Task-Id: FN-4951
Fusion-Task-Lineage: 25de66db-c8cf-463b-86f2-efff1bc22683

packages/dashboard/app/utils/copyToClipboard.ts

@@ -0,0 +1,41 @@
+export async function copyTextToClipboard(text: string): Promise<boolean> {
+  if (
+    typeof navigator !== "undefined" &&
+    typeof window !== "undefined" &&
+    window.isSecureContext !== false &&
+    navigator.clipboard?.writeText
+  ) {
+    try {
+      await navigator.clipboard.writeText(text);
+      return true;
+    } catch {
+      // Fall through to execCommand fallback.
+    }
+  }
+
+  if (typeof document === "undefined" || !document.body) {
+    return false;
+  }
+
+  const textarea = document.createElement("textarea");
+  textarea.value = text;
+  textarea.setAttribute("readonly", "");
+  textarea.style.position = "fixed";
+  textarea.style.left = "-9999px";
+  textarea.style.top = "0";
+  textarea.style.opacity = "0";
+  textarea.style.pointerEvents = "none";
+
+  document.body.appendChild(textarea);
+
+  try {
+    textarea.focus();
+    textarea.select();
+    textarea.setSelectionRange(0, text.length);
+    return document.execCommand("copy");
+  } catch {
+    return false;
+  } finally {
+    textarea.remove();
+  }
+}