chore: add pipenv dependency and lock

Adding pipenv as a dependency to the pipenv environment itself is admittedly
counter-intuitive, however this gives the advantage of being able to install all
dependencies (including dev-dependencies) via the common and generally available
`pip` package manager interface. The generation of requirements.txt and
requirements-dev.txt is abstracted through the Makefile.

Pipfile

@@ -12,7 +12,7 @@ tox = "~=4.24.2"
 mypy = "~=1.15.0"
 autopep8 = "~=2.3.2"
 setuptools-scm = "~=8.2.0"
-pipenv = "*"
+pipenv = "~=2024.4.1"
 
 [requires]
 python_version = "3.11"

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "7a4671ceb800ea54b1f9c0f7f65262fa321f85decd8a0e865199d3c768122098"
+            "sha256": "993ac222de569f8a8d09bd369675a8dbaaa6e6d5ecad45ed341a14945b95c4b3"
         },
         "pipfile-spec": 6,
         "requires": {