Add pyproject.toml to Django apps that are part of a source tree

Question

I have a Django application which consists of two Django 'apps' - the term used in the Django world for (potentially) reusable packages. My whole application lives in one git repository. I would like to use one of the apps in another Python application. Specifically, I want to use the Django ORM and need to use the models definied in that app. Currently I put the parent directory of the app onto my sys.path and it works fine. But I would like to be able to pip install that app.

My directory layout looks like this:

website/
  website/  <- main Django app
    settings.py
    urls.py
    ...
  crawls/   <- app I want to share
    views.py
    urls.py
    pyproject.toml  <- this is new
    ...
other_app/   <- application where I want to use `crawls`

What I tried now is to place a pyproject.toml into crawls. However, both hatchling and flit seem to insist on an additional subdirectory. For example, the following results in ValueError: No file/folder found for module gen_crawler_crawls:

[build-system]
requires = ["flit_core >=3.2,<4"]
build-backend = "flit_core.buildapi"

[project]
name = "gen-crawler-crawls"
dependencies = [
  "Django>=5.0.6",
]
requires-python = ">=3.12"
authors = [
  {name = "Homer Simpson", email = "homer.simpson@example.com"},
]
dynamic = ["version", "description"]

So, how do I make crawls into a installable package without adding another directory layer (which would break my main app)? Or is there an alternative way to package this?