Allow empty password in Connect and Discover dialogs

Some devices have no password configured, so only username is required.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

connect_dialog.py

@@ -96,9 +96,6 @@ class ConnectDialog:
         if not user:
             self._status_label.config(text="Username is required", foreground="#c00000")
             return
-        if not password:
-            self._status_label.config(text="Password is required", foreground="#c00000")
-            return
 
         try:
             port_int = int(port)
@@ -393,9 +390,6 @@ class _CredentialsDialog:
         if not user:
             self._status_label.config(text="Username is required", foreground="#c00000")
             return
-        if not password:
-            self._status_label.config(text="Password is required", foreground="#c00000")
-            return
 
         try:
             port_int = int(self._port)