feat(prefect-worker): add git for cloning flow repositories

Git is required by Prefect workers to pull flow code from remote
repositories before execution.

images/prefect-worker-pg-backup/Dockerfile

@@ -11,9 +11,12 @@ LABEL maintainer="Damien Arnodo"
 LABEL org.opencontainers.image.title="Prefect Worker - PostgreSQL Backup"
 LABEL org.opencontainers.image.description="Prefect worker with PostgreSQL and S3 tools for database backups"
 
-# Installation des outils PostgreSQL (pg_dump, pg_restore, etc.)
+# Installation des outils système
+# - postgresql-client : pg_dump, pg_restore, psql
+# - git : nécessaire pour cloner les repositories contenant le code des flows
 RUN apt-get update && apt-get install -y --no-install-recommends \
     postgresql-client \
+    git \
     && rm -rf /var/lib/apt/lists/*
 
 # Installation des dépendances Python pour S3 et PostgreSQL