I've had my first successful test of the feeder Web interface.  After powering on the below contraption, I'm able to both capture still images from the camera and issue a web request that triggers the rotation of the motor by a set number of scoops.

Most of the web code is cribbed together from the ESP32 CameraWebServer example and the UPnP SimpleServerESP32 example, but the motor control and switch sensor code for actually operating the feeder are completely from scratch.

I've completely disconnected the battery compartment and added a buck converter to step down from 12v to 5v, since I have both a ridiculous number of 12v power adapters and quite a few buck converters laying around.  Now I just have to re-assemble this into a functional piece of hardware.