Copy file to iPhone app from Mac OS terminal
The feature you are looking for is called iOS File Sharing. You can copy files from macOS into an iOS app installed on iPhone/iPad if the iOS app supports File Sharing.
To copy files into an iOS app that supports File Sharing, you'd need to connect your iOS device to your Mac, and access the device via iTunes app (macOS Mojave and earlier) or Finder app (macOS Catalina and later)
Refer to the linked Apple Support document for detailed instructions:

macOS Mojave 10.14 and earlier:
https://support.apple.com/kb/HT201301

macOS Catalina 10.15 and later:
https://support.apple.com/kb/HT210598