refactor: add phpstan and update code to adhere to level 5

- move and refactor Image.php from Libraries to Entities folder
- update some database field names
/ types
- update composer packages

tests/_support/SessionTestCase.php

@@ -6,6 +6,9 @@ use CodeIgniter\Test\CIUnitTestCase;
 use CodeIgniter\Test\Mock\MockSession;
 use Config\Services;
 
+/**
+ * @phpstan-ignore-next-line
+ */
 class SessionTestCase extends CIUnitTestCase
 {
     /**