Logout

OAuth2 logout endpoint. Logs out the user from Auth0 and redirects to specified URL.

**Query Parameters:**
- `returnTo`: URL to redirect to after logout (optional, default: extension logout page)
- `client_type`: Client type for determining Auth0 client ID (optional, default: papr_plugin)

**Flow:**
1. Client redirects user to this endpoint
2. This endpoint redirects to Auth0 logout URL
3. Auth0 logs out the user and redirects to the specified return URL

**Example:**
```
GET /logout?returnTo=https://chat.openai.com
```

**Note:** This endpoint initiates the logout process. The actual logout completion happens on Auth0's side.