Revert "fix: remove class-level .env rename in EncryptionTest to prevent test pollution"

This reverts commit 9fdc43e.

Author: gr8man

tests/system/Encryption/EncryptionTest.php

@@ -35,9 +35,13 @@ public static function setUpBeforeClass(): void
 
         CodeIgniterServices::injectMock('superglobals', new Superglobals());
 
-        putenv('encryption.key');
-        unset($_ENV['encryption.key']);
-        service('superglobals')->unsetServer('encryption.key');
+        if (is_file(ROOTPATH . '.env')) {
+            rename(ROOTPATH . '.env', ROOTPATH . '.env.bak');
+
+            putenv('encryption.key');
+            unset($_ENV['encryption.key']);
+            service('superglobals')->unsetServer('encryption.key');
+        }
     }
 
     protected function setUp(): void
@@ -47,6 +51,15 @@ protected function setUp(): void
         $this->encryption = new Encryption();
     }
 
+    public static function tearDownAfterClass(): void
+    {
+        parent::tearDownAfterClass();
+
+        if (is_file(ROOTPATH . '.env.bak')) {
+            rename(ROOTPATH . '.env.bak', ROOTPATH . '.env');
+        }
+    }
+
     /**
      * Covers behavior with config encryption key set or not
      */