stereo-gui: move away from hardcoded IP addresses

We are currently using a hardcoded IP address for the right camera in left.py. This is not optimal as this needs to be changed every time the right camera's IP address changes. We should probably move towards using auto discovery using something like mDNS.

Start with left.py and locate where the right camera's IP address is hardcoded. Investigate auto-discovery using mDNS or a similar approach, then verify that changing the camera's IP no longer requires editing the file.

Written by the indexing model from the issue text.