2023-11-26T14:32:23.502 app[2865339fe20568] dfw [info] npm ERR! enoent Could not read package.json: Error: ENOENT: no such file or directory, open ‘/package.json’
2023-11-26T14:32:23.502 app[2865339fe20568] dfw [info] npm ERR! enoent This is related to npm not being able to find a file.
2023-11-26T14:32:23.504 app[2865339fe20568] dfw [info] npm ERR! A complete log of this run can be found in: /root/.npm/_logs/2023-11-26T14_32_23_262Z-debug-0.log
Note that there is a leading slash in this line. Something you are running is looking for package.json is the root directory of the file system.
The way I typically debug these types of situations is to run fly console which will launch an ephemeral machine and you will be logged in as root. From there you can look around, and run commands.