fix: replace VENV -> VENV_DIR

Makefile

@@ -3,8 +3,8 @@ IMAGE_NAME ?= ai-dial-adapter-vertexai
 PLATFORM ?= linux/amd64
 DEV_PYTHON ?= 3.11
 DOCKER ?= docker
-VENV ?= .venv
-POETRY ?= ${VENV}/bin/poetry
+VENV_DIR ?= .venv
+POETRY ?= $(VENV_DIR)/bin/poetry
 POETRY_VERSION ?= 1.8.5
 ARGS=
 
@@ -13,36 +13,36 @@ ARGS=
 all: build
 
 init_env:
-	python -m venv ${VENV}
-	${VENV}/bin/pip install poetry==${POETRY_VERSION} --quiet
+	python -m venv $(VENV_DIR)
+	$(VENV_DIR)/bin/pip install poetry==$(POETRY_VERSION) --quiet
 
 install: init_env
-	${POETRY} env use python$(DEV_PYTHON)
-	${POETRY} install
+	$(POETRY) env use python$(DEV_PYTHON)
+	$(POETRY) install
 
 build: install
-	${POETRY} build
+	$(POETRY) build
 
 serve: install
-	${POETRY} run uvicorn "aidial_adapter_vertexai.app:app" \
+	$(POETRY) run uvicorn "aidial_adapter_vertexai.app:app" \
 		--reload --host "0.0.0.0" --port $(PORT) \
 		--workers=1 --env-file ./.env
 
 clean:
-	${POETRY} run python -m scripts.clean
-	${POETRY} env remove --all
+	$(POETRY) run python -m scripts.clean
+	$(POETRY) env remove --all
 
 lint: install
-	${POETRY} run nox -s lint
+	$(POETRY) run nox -s lint
 
 format: install
-	${POETRY} run nox -s format
+	$(POETRY) run nox -s format
 
 test: install
-	${POETRY} run nox -s test
+	$(POETRY) run nox -s test
 
 integration_tests: install
-	${POETRY} run nox -s integration_tests
+	$(POETRY) run nox -s integration_tests
 
 docker_test:
 	$(DOCKER) build --platform $(PLATFORM) -f Dockerfile.test -t $(IMAGE_NAME):test .