feat: integrate Pi backend and Pi Web

pi-web/lib/clipboard.ts

@@ -0,0 +1,18 @@
+export function copyText(text: string): Promise<void> {
+  if (navigator.clipboard?.writeText) {
+    return navigator.clipboard.writeText(text);
+  }
+  try {
+    const ta = document.createElement("textarea");
+    ta.value = text;
+    ta.style.position = "fixed";
+    ta.style.opacity = "0";
+    document.body.appendChild(ta);
+    ta.select();
+    document.execCommand("copy");
+    document.body.removeChild(ta);
+    return Promise.resolve();
+  } catch {
+    return Promise.reject();
+  }
+}