test: fix password mismatch test to use valid complex passwords

The test was using simple passwords ('password1', 'password2') that
failed complexity validation before the mismatch check could run.

Changed to use valid complex passwords that don't match:
- new_password: 'NewPassword123!'
- confirm_password: 'DifferentPass123!'

This properly tests the mismatch validation path. All 4 subtests in
TestUpdatePasswordAdminMode now pass.

cmd/server/tests/user_test.go

@@ -361,8 +361,8 @@ func TestUpdatePasswordAdminMode(t *testing.T) {
 		targetUser := createRegularUserOnce(t, setup.DB)
 
 		jsonData, _ := json.Marshal(map[string]interface{}{
-			"new_password":     "password1",
-			"confirm_password": "password2",
+			"new_password":     "NewPassword123!",
+			"confirm_password": "DifferentPass123!",
 		})
 
 		req := httptest.NewRequest("PUT", "/api/auth/password/"+targetUser.ID.String(), bytes.NewBuffer(jsonData))