I've learned something, thanks

Read the voltage on ao and google code for steinhart equation. The lm393 is not needed.

I store the app bin files on a nas drive and upload them via a browser on my tablet

Switching apps is easy with web ota if waiting 30 secs is ok, the problem was wearing out the flash, but even reflashing several times a day ends up not being an issue so I didn't bother with external flash.

I was recently researching something similar. If its a one-off, flash is cheap, so you could connect external flash by modifying the efuses and replace it when its worn.
https://esp32.com/viewtopic.php?f=12&t=2884

In the Arduino IDE tools menu dropdown

As above, disconnect pin 12 and try again. I avoid pin 12 if I can.

Memory problems tend to cause crashes rather than hangs. I once had an annoying hang from corruption by a buffer overflow due to my sloppy coding.

If it is client side rendered then view the page source and paste it into a string which you can serve up from the esp32

Investigating a problem with a script not outputting high on pin 15, I found that the problem (feature?) was caused by the WiFi library (Arduino IDE) pulling the pin low, possibly associated with wifi event handling. This can be demonstrated using the example script WiFiClientEvents and adding a dig...