backend: move gui/backends.py to backend/serial.py

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

backend/serial.py

@@ -3,10 +3,8 @@ from threading import Thread
 from queue    import Queue, Empty
 
 _root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-_gui  = os.path.dirname(os.path.abspath(__file__))
-for _p in [_root, _gui]:
-    if _p not in sys.path:
-        sys.path.insert(0, _p)
+if _root not in sys.path:
+    sys.path.insert(0, _root)
 
 from backend.a_backend import ABackend
 from a_transceiver import ATransceiver

gui/data_model.py

@@ -147,7 +147,7 @@ class ReceiverManager(QObject):
 
     def connect_receiver(self, rid: str):
         from listeners import NavSatQtListener, GsaQtListener
-        from backends  import SerialBackend
+        from backend.serial import SerialBackend
 
         config = self._configs.get(rid)
         state  = self._states.get(rid)