chore(deps): bump actions/checkout from 4 to 7

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 7.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v7)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/airflow.yml

@@ -47,7 +47,7 @@ jobs:
 
     steps:
       - name: Récupère le dépôt
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Installe uv
         uses: astral-sh/setup-uv@v5
@@ -78,7 +78,7 @@ jobs:
 
     steps:
       - name: Récupère le dépôt
-        uses: actions/checkout@v4
+        uses: actions/checkout@v7
 
       - name: Construit l'image (contexte à la racine, elle COPY ml/ et apps/backend/)
         run: docker build -f etl/airflow/Dockerfile -t enervision-airflow:ci .