test: fix password similarity test case

- Correct validate() method call to include both password and username parameters
- Previously passing null for username prevented similarity check from executing
- Now properly tests password-to-username similarity validation

This ensures the similarity check test actually validates the intended behavior.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: devondragon

src/test/java/com/digitalsanctuary/spring/user/service/PasswordPolicyServiceTest.java

@@ -255,7 +255,7 @@ void validate_rejectsWhenSimilarityAboveThreshold() {
                 .thenReturn("password.error.similarity");
 
         // Identical strings => 100% similarity >= 80 -> fail
-        List<String> errors = service.validate(null, "password", null, LOCALE);
+        List<String> errors = service.validate(null, "password", "password", LOCALE);
 
         assertEquals(1, errors.size());
         assertEquals("password.error.similarity", errors.get(0));