Fix dependency issue

[smcmurtry]

Summary | Résumé

Fix dependency issue - builds have failed since monday, this should fix the build error: https://github.com/cds-snc/notification-api/actions/runs/23490450868/job/68547058126

I tested locally with:

docker build \
  --build-arg GIT_SHA=$(git rev-parse --short HEAD) \
  -f ci/Dockerfile.lambda \
  -t api-lambda:test \
  .

And it built successfully.

Release Instructions | Instructions pour le déploiement

None.

Reviewer checklist | Liste de vérification du réviseur

• This PR does not break existing functionality.
• This PR does not violate GCNotify's privacy policies.
• This PR does not raise new security concerns. Refer to our GC Notify Risk Register document on our Google drive.
• This PR does not significantly alter performance.
• Additional required documentation resulting of these changes is covered (such as the README, setup instructions, a related ADR or the technical documentation).

⚠ If boxes cannot be checked off before merging the PR, they should be moved to the "Release Instructions" section with appropriate steps required to verify before release. For example, changes to celery code may require tests on staging to verify that performance has not been affected.

[Copilot]

Pull request overview

This PR aims to fix CI/docker build failures for the Lambda image by adjusting how Poetry dependencies and Lambda runtime dependencies are installed.

Changes:

• Copies README.md alongside pyproject.toml/poetry.lock during the dependency-install layer.
• Replaces poetry add awslambdaric wheel with a direct pip install awslambdaric during image build.

---

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[Copilot]

Including README.md in the dependency-layer COPY means any README change will invalidate Docker cache and force a full dependency reinstall. If the only reason for copying it is to satisfy readme = "README.md" during poetry install, consider switching this step to poetry install --no-root (or otherwise avoiding installing the project package in this layer) so the deps layer can stay independent of README edits.

Suggested change

	COPY pyproject.toml poetry.lock README.md ${TASK_ROOT}/
	# Install Poetry dependencies first (including setuptools and wheel)
	RUN python -m venv ${APP_VENV} \
	&& . ${APP_VENV}/bin/activate \
	&& poetry install \
	COPY pyproject.toml poetry.lock ${TASK_ROOT}/
	# Install Poetry dependencies first (including setuptools and wheel)
	RUN python -m venv ${APP_VENV} \
	&& . ${APP_VENV}/bin/activate \
	&& poetry install --no-root \