fix: Remove await from synchronous Modbus client connect call

The Modbus client connect method is synchronous, not async

src/dashboard/api.py

@@ -728,7 +728,7 @@ async def get_signals():
         )
         
         # Connect to Modbus server
-        if await modbus_client.connect():
+        if modbus_client.connect():
             logger.info("using_real_modbus_data")
             
             # Read pump data from Modbus server