I have built two of these for dogs. It's really not hard,w hether you go completely from scratch or use something premade.

If you want something mostly premade,go get an autoslide. If you want to do it completely from scratch:

1. RFID/bluetooth proximity is much easier to work with than camera + rpi + AI. For the usecase you are talking about, AI is not just overkill, but will make it actively harder to achieve your goal

2. Locking is pretty easy depending on motor mechanism - either a cheap relay'd magnetic lock, or simply a motor that can't be backdriven easily.

Motor wise, you can either use the rack and pinion style that autoslide does, or a simple linear motor if you don't want to deal with gear tracks.

Overall, i went the autoslide route and had it all set up and working in an hour or two.