add error handling for serial connection failures to GRBLHandler

robot-control/src/api/grbl_handler.py

@@ -30,10 +30,14 @@ class GRBLHandler:
             return
 
         logger.info("Connecting to GRBL...")
-        self.reader, self.writer = await serial_asyncio.open_serial_connection(
-            url = self.port,
-            baudrate = self.baudrate
-        )
+        try:
+            self.reader, self.writer = await serial_asyncio.open_serial_connection(
+                url = self.port,
+                baudrate = self.baudrate
+            )            
+        except serial_asyncio.serial.SerialException as e:
+            raise serial_asyncio.serial.SerialException(f"Failed to connect to robot: {str(e)}")
+
         init_response = []
         for _ in range(3): # Flush initial responses
             init_response.append(await self._process_response())