fix(tests): Fix encryption test isolation between test runs

Add global encryption teardown to TestCase base class so encryption state
does not leak between test suites regardless of which tests ran earlier.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Stephen Cuppett <steve@cuppett.com>

Author: cuppett

tests/lib/TestCase.php

@@ -27,6 +27,7 @@
 use OCP\Command\IBus;
 use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\Files\IRootFolder;
+use OCP\IAppConfig;
 use OCP\IConfig;
 use OCP\IDBConnection;
 use OCP\IUserManager;
@@ -195,6 +196,22 @@ protected function tearDown(): void {
 				call_user_func([$this, $methodName]);
 			}
 		}
+
+		// Clean up encryption state to prevent test pollution
+		// This ensures encryption_enabled is reset after each test, preventing
+		// MultiKeyEncryptException failures in subsequent tests when encryption
+		// is left enabled but user keys don't exist
+		try {
+			$appConfig = Server::get(IAppConfig::class);
+			$currentValue = $appConfig->getValueBool('core', 'encryption_enabled', false);
+			if ($currentValue) {
+				$appConfig->setValueBool('core', 'encryption_enabled', false);
+				$appConfig->deleteKey('core', 'default_encryption_module');
+				$appConfig->deleteKey('encryption', 'useMasterKey');
+			}
+		} catch (\Throwable $e) {
+			// Ignore - may be called before bootstrap completes
+		}
 	}
 
 	/**