docs: add TOTP setup instructions to user documentation (#9843)

Signed-off-by: Thomas Moraine <thomas.moraine@vates.tech>

docs/docs/xo5/users.md

@@ -33,6 +33,32 @@ This is the default method. Creating a user is very simple:
 
 By default, a _user_ won't have any permissions. At the opposite, an _admin_ will have all rights.
 
+#### OTP Authentication (2FA)
+
+Xen Orchestra supports **Time-based One-Time Password (TOTP)** to provide an additional layer of security for your user account. When enabled, you will be required to provide a temporary code from an authentication app in addition to your standard credentials during login.
+
+##### Enabling TOTP
+
+To activate two-factor authentication on your account:
+
+1. Go to your profile settings.
+2. At the top of the screen, go to the **OTP authentication** field and toggle the switch to the **On** position.
+    ![User configuration form](../assets/totp-config.png)
+3. A window will appear displaying a **QR code**:
+    ![QR code for enabling TOTP on a user account](../assets/toptp-qr-code.png)
+4. Open your preferred authentication app on your mobile device and **scan the QR code**.
+5. The app will generate a temporary 6-digit code.
+6. Enter this code into the **OTP code** field in the Xen Orchestra window.
+7. Click **OK** to validate and finalize the activation.
+
+:::note
+Once activated, any future login attempts will prompt you for a new code generated by your application.
+:::
+
+##### Disabling TOTP
+
+To disable this feature, return to your profile settings and toggle the **OTP authentication** switch to **Off**. You will be asked to provide a final OTP code to confirm the deactivation.
+
 ### LDAP
 
 XO currently supports connections to LDAP directories, like _Open LDAP_ or _Active Directory_.