Fix fatal error: WP_REST_Server::get_request() does not exist

Store authenticated user ID on the auth object instance instead of
trying to retrieve it from the REST server request. This was the root
cause of all mobile API 500 errors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/class-twp-mobile-auth.php

@@ -9,6 +9,7 @@ class TWP_Mobile_Auth {
     private $secret_key;
     private $token_expiry = 86400; // 24 hours in seconds
     private $refresh_expiry = 2592000; // 30 days in seconds
+    private $current_user_id = null;
 
     /**
      * Constructor
@@ -330,7 +331,7 @@ class TWP_Mobile_Auth {
         }
 
         // Store user ID for later use
-        $request->set_param('_twp_user_id', $payload->user_id);
+        $this->current_user_id = $payload->user_id;
 
         return true;
     }
@@ -339,8 +340,7 @@ class TWP_Mobile_Auth {
      * Get current user ID from token
      */
     public function get_current_user_id() {
-        $request = rest_get_server()->get_request();
-        return $request->get_param('_twp_user_id');
+        return $this->current_user_id;
     }
 
     /**