test(behat): reset per-scenario state in BasicStructure and Sharing

Add @BeforeScenario hooks to reset auth/server state and sharing state
between scenarios, preventing state bleed across test runs.

- BasicStructure: reset currentUser, currentServer, baseUrl, apiVersion,
  requestToken and cookieJar (baseUrl and currentServer go together via
  usingServer(), so both must be reset)
- Sharing: reset lastShareData, storedShareData and savedShareId

Signed-off-by: Anna Larch <anna@nextcloud.com>
AI-Assisted-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: miaulalala

build/integration/features/bootstrap/BasicStructure.php

@@ -72,6 +72,18 @@ public function __construct($baseUrl, $admin, $regular_user_password) {
 		}
 	}
 
+	/**
+	 * @BeforeScenario
+	 */
+	public function resetAuthState(): void {
+		$this->currentUser = '';
+		$this->currentServer = 'LOCAL';
+		$this->baseUrl = $this->localBaseUrl;
+		$this->apiVersion = 1;
+		$this->requestToken = null;
+		$this->cookieJar = new CookieJar();
+	}
+
 	/**
 	 * @Given /^using api version "(\d+)"$/
 	 */

build/integration/features/bootstrap/Sharing.php

@@ -23,6 +23,15 @@ trait Sharing {
 	/** @var SimpleXMLElement[] */
 	private array $storedShareData = [];
 	private ?string $savedShareId = null;
+
+	/**
+	 * @BeforeScenario
+	 */
+	public function resetSharingState(): void {
+		$this->lastShareData = null;
+		$this->storedShareData = [];
+		$this->savedShareId = null;
+	}
 	/** @var ResponseInterface */
 	private $response;