Enable WebAuthn Passkeys

a, _ := theauth.New(theauth.Config{
    Storage: store,
    BaseURL: "https://myapp.com",
    WebAuthn: &theauth.WebAuthnConfig{
        RPDisplayName: "My App",
        RPID:          "myapp.com",       // must match the domain; no port, no scheme
        RPOrigins:     []string{"https://myapp.com"},
    },
})

// 1. Get challenge from server
const beginResp = await fetch('/auth/webauthn/register/begin', { method: 'POST' });
const options = await beginResp.json();

// 2. Call browser WebAuthn API
const credential = await navigator.credentials.create({ publicKey: options });

// 3. Send credential back to server
await fetch('/auth/webauthn/register/finish', {
    method: 'POST',
    body: JSON.stringify(credential),
    headers: { 'Content-Type': 'application/json' },
});

// 1. Get challenge (no username required)
const beginResp = await fetch('/auth/webauthn/login/begin', { method: 'POST' });
const options = await beginResp.json();

// 2. Call browser WebAuthn API (user selects passkey in browser UI)
const assertion = await navigator.credentials.get({ publicKey: options });

// 3. Send assertion to server
const finishResp = await fetch('/auth/webauthn/login/finish', {
    method: 'POST',
    body: JSON.stringify(assertion),
    headers: { 'Content-Type': 'application/json' },
});