Fix Django shell command crash with functions

[archie-ai-code-explain-pr-review]

• The python -m django shell -c command crashes when passing Python code with functions, while the python -c command works fine.
• The issue is in the usage of exec in the handle method of the django.core.management.commands.shell.Command class.
• The error message shows that the django module is not defined in the context of the exec call, causing a NameError.
• The solution is to pass a dictionary containing a minimal set of globals as the second argument to exec, instead of relying on the default global context.