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>

docs/PROGRESS.md

@@ -175,6 +175,15 @@ Delivered:
   cleanly rather than sending Apple auth a blank username. The value is
   kept on the tab's in-memory profile copy for its lifetime, not written
   back to the saved profile
+- The blank-username relaxation above initially only covered
+  `ProfileDialog`'s own save-time validation; `ProfileRepository::
+  isProfileValid()` had the identical "username required for SSH/RDP"
+  check independently, called directly by `insertProfile()`/
+  `updateProfile()` -- which is exactly the path mRemoteNG import uses
+  (it builds `Profile` objects and inserts them directly, never going
+  through the dialog), so importing any SSH/RDP entry without a
+  username still failed outright until this second check was found and
+  removed too
 - Robustness fix: an unrecognized `FramebufferUpdate` rectangle encoding
   used to abort the connection generically; `kAnnouncedEncodings` is now
   the single source of truth for what `SetEncodings` announces and what