Move the generic camera keywords into the shared camera_daemon service

[mikelangmayr]

• daemons/generic/camera composes camera_daemon.CameraService instead of implementing the generic keywords itself, dropping it from 276 lines to 80
• The service is reusable by projects with their own libby base, which a shared daemon class could not be, since each project fixes its own transport and broker
• Loading the instrument stays here, because it resolves a dotted path into this repo's namespace, and it runs before connect, which reads camera_class off it
• The service assigns camera on the daemon, so tracking_camera/keywords.py is unchanged
• No behaviour change: the same 11 generic keywords register, and the tracking camera still adds its own on top
• Verified by constructing the daemon and registering the full keyword set; pylint 10.00/10