fix: preserve PDODB_USERNAME and PDODB_PASSWORD in OptimizeCommandCliTests tearDown

Fixed issue where OptimizeCommandCliTests::tearDown() was clearing
PDODB_USERNAME and PDODB_PASSWORD environment variables, causing
subsequent tests to fail with 'Login failed for user testuser' error.

The problem occurred because:
1. OptimizeCommandCliTests runs and sets environment variables in setUp()
2. tearDown() clears all environment variables including PDODB_USERNAME/PASSWORD
3. Subsequent tests that create new connections cannot read credentials
4. They fall back to default testuser/testpass which don't exist in CI

Solution:
- Keep PDODB_USERNAME and PDODB_PASSWORD in tearDown() as they are
  needed by other tests that may create new PdoDb instances
- Only clear test-specific variables (DRIVER, HOST, PORT, DATABASE)

This ensures that environment variables from GitHub Actions (sa/Test123!@#)
remain available for all tests throughout the test suite execution.

Author: tommyknocker

tests/mssql/OptimizeCommandCliTests.php

@@ -38,12 +38,15 @@ public function setUp(): void
     public function tearDown(): void
     {
         // Clean up environment variables to avoid affecting other tests
+        // Note: Do not clear PDODB_USERNAME and PDODB_PASSWORD as they are needed
+        // by other tests that may create new connections
         putenv('PDODB_DRIVER');
         putenv('PDODB_HOST');
         putenv('PDODB_PORT');
         putenv('PDODB_DATABASE');
-        putenv('PDODB_USERNAME');
-        putenv('PDODB_PASSWORD');
+        // Keep PDODB_USERNAME and PDODB_PASSWORD for other tests
+        // putenv('PDODB_USERNAME');
+        // putenv('PDODB_PASSWORD');
         putenv('PDODB_NON_INTERACTIVE');
         parent::tearDown();
     }