add passkey support

static/passkey-login.js

@@ -0,0 +1,38 @@
+function b64ToBytes(b64) {
+  const bin = atob(b64.replace(/-/g, "+").replace(/_/g, "/"));
+  const bytes = new Uint8Array(bin.length);
+  for (let i = 0; i < bin.length; i++) bytes[i] = bin.charCodeAt(i);
+  return bytes;
+}
+
+document.getElementById("passkey-login").addEventListener("click", async () => {
+  const email = document.getElementById("email").value;
+  if (!email) {
+    alert("Enter your email first.");
+    return;
+  }
+  const start = await fetch("/auth/passkey/login/start", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ email }),
+  });
+  if (!start.ok) {
+    alert("No passkey found for that email.");
+    return;
+  }
+  const options = await start.json();
+  const pk = options.publicKey;
+  pk.challenge = b64ToBytes(pk.challenge);
+  if (pk.allowCredentials) {
+    pk.allowCredentials.forEach((c) => (c.id = b64ToBytes(c.id)));
+  }
+  const credential = await navigator.credentials.get(options);
+  const finish = await fetch("/auth/passkey/login/finish", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ response: credential }),
+  });
+  if (finish.ok) {
+    window.location.href = "/lists";
+  }
+});