[platform]: fix migrations (#840)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Chores**
	- Updated installer image to include additional system utilities.
- Migration scripts now update Kubernetes ConfigMap with the current
stack version for improved version tracking.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/core/installer/images/cozystack/Dockerfile

@@ -31,6 +31,7 @@ FROM alpine:3.21
 RUN apk add --no-cache make
 RUN apk add helm kubectl --repository=https://dl-cdn.alpinelinux.org/alpine/edge/community
 RUN apk add yq
+RUN apk add coreutils
 
 COPY scripts /cozystack/scripts
 COPY --from=builder /src/packages/core /cozystack/packages/core

scripts/migrations/10

@@ -10,3 +10,6 @@ if kubectl get helmrelease keycloak-configure -n cozy-keycloak; then
     reconcile.fluxcd.io/requestedAt="$timestamp" \
     --overwrite
 fi
+
+# Write version to cozystack-version config
+kubectl create configmap -n cozy-system cozystack-version --from-literal=version=11 --dry-run=client -o yaml | kubectl apply -f-

scripts/migrations/11

@@ -16,3 +16,6 @@ if kubectl get helmrelease monitoring-agents -n cozy-monitoring; then
 fi
 
 kubectl delete pods -l app.kubernetes.io/component=kube-rbac-proxy -n cozy-monitoring
+
+# Write version to cozystack-version config
+kubectl create configmap -n cozy-system cozystack-version --from-literal=version=12 --dry-run=client -o yaml | kubectl apply -f-