Fix mRemoteNG import failing on entries without a username

The previous username relaxation only touched ProfileDialog's own
save-time validation. ProfileRepository::isProfileValid() had the
identical "username required for SSH/RDP" check independently, called
directly by insertProfile()/updateProfile() -- exactly the path
mRemoteNG import uses, since it builds Profile objects and inserts
them directly rather than going through the dialog. Every imported
SSH/RDP entry without a recorded username was rejected outright.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/test_profile_repository.cpp

@@ -48,7 +48,7 @@ private slots:
     void createProfileRejectsMissingName();
     void createProfileRejectsMissingHost();
     void createProfileRejectsInvalidPort();
-    void createProfileRejectsMissingUsernameForSsh();
+    void createProfileAllowsMissingUsernameForSsh();
     void createProfileRejectsMissingPrivateKeyForKeyAuth();
     void createProfileRejectsDuplicateName();
     void updateProfilePersistsChanges();
@@ -156,11 +156,17 @@ void TestProfileRepository::createProfileRejectsInvalidPort()
     QVERIFY(!m_repo->createProfile(profile).has_value());
 }
 
-void TestProfileRepository::createProfileRejectsMissingUsernameForSsh()
+void TestProfileRepository::createProfileAllowsMissingUsernameForSsh()
 {
+    // SSH/RDP no longer require a username at save time (issue #21) --
+    // among other things, this unblocks importing mRemoteNG entries that
+    // don't have one recorded, which used to fail outright. The user is
+    // asked for it at connect time instead (see SessionTab).
     Profile profile = makeSshProfile();
     profile.username.clear();
-    QVERIFY(!m_repo->createProfile(profile).has_value());
+    const auto created = m_repo->createProfile(profile);
+    QVERIFY(created.has_value());
+    QVERIFY(created->username.isEmpty());
 }
 
 void TestProfileRepository::createProfileRejectsMissingPrivateKeyForKeyAuth()