fix(installer): bootstrap cozy-system via --create-namespace + label hook

Removes the chart's `Namespace cozy-system` resource and replaces it with
a pre-install/pre-upgrade Job hook (cozy-system-labeler) that patches the
required labels onto the namespace after `--create-namespace` creates it.

Why: helm v3 has a known chicken-and-egg with charts that ship their own
Namespace:
  - WITH `--create-namespace` on the install command, helm pre-creates the
    namespace via plain kubectl-create (no helm meta annotations); the
    chart's own Namespace apply then fails with `already exists`.
  - WITHOUT `--create-namespace`, helm fails immediately because it cannot
    write its release-secret to a non-existent namespace.

Until now this was hidden by the 3x retry on `Install Cozystack` in
`.github/workflows/pull-requests.yaml`: first attempt always fails with
the conflict, second attempt sees the existing failed release and takes
the upgrade code path which patch-merges instead of strict-create.
Reproducible on every cold install. Surfaced cleanly when retries on the
install step were dropped.

After this change:
  - install commands use `helm upgrade --install --namespace cozy-system
    --create-namespace`. Standard pattern, matches kube-prometheus-stack /
    argo-cd / cert-manager / others.
  - the pre-install hook (SA + ClusterRole + ClusterRoleBinding + Job)
    patches `cozystack.io/system=true` and
    `pod-security.kubernetes.io/enforce=privileged` onto the namespace
    before main resources apply.
  - hook-delete-policy=before-hook-creation,hook-succeeded so the RBAC
    surface only exists during install/upgrade.

Verified end-to-end on a kind cluster: cold install in 3.3s, upgrade
idempotent, cleanup clean. Image pinned to `alpine/k8s:1.32.0` for the
hook (small, public, includes kubectl).

Signed-off-by: Myasnikov Daniil <myasnikovdaniil2001@gmail.com>

packages/core/installer/templates/cozy-system-labels.yaml

@@ -0,0 +1,82 @@
+{{/*
+  Pre-install/upgrade hook that labels the cozy-system namespace with the
+  PodSecurity and cozystack identity labels. The chart no longer ships a
+  Namespace resource (helm v3 cannot adopt a namespace pre-created by
+  --create-namespace because it lacks helm meta annotations; without
+  --create-namespace, helm fails to write its release-secret because the
+  namespace does not exist yet — chicken-and-egg).
+  Install commands now use --create-namespace to bootstrap the namespace,
+  and this hook patches the labels the operator depends on (notably
+  pod-security.kubernetes.io/enforce=privileged for the host-network
+  operator pod).
+*/}}
+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: cozy-system-labeler
+  namespace: cozy-system
+  annotations:
+    helm.sh/hook: pre-install,pre-upgrade
+    helm.sh/hook-weight: "-200"
+    helm.sh/hook-delete-policy: before-hook-creation,hook-succeeded
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: cozy-system-labeler
+  annotations:
+    helm.sh/hook: pre-install,pre-upgrade
+    helm.sh/hook-weight: "-180"
+    helm.sh/hook-delete-policy: before-hook-creation,hook-succeeded
+rules:
+- apiGroups: [""]
+  resources: ["namespaces"]
+  resourceNames: ["cozy-system"]
+  verbs: ["get", "patch"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: cozy-system-labeler
+  annotations:
+    helm.sh/hook: pre-install,pre-upgrade
+    helm.sh/hook-weight: "-160"
+    helm.sh/hook-delete-policy: before-hook-creation,hook-succeeded
+subjects:
+- kind: ServiceAccount
+  name: cozy-system-labeler
+  namespace: cozy-system
+roleRef:
+  kind: ClusterRole
+  name: cozy-system-labeler
+  apiGroup: rbac.authorization.k8s.io
+---
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: cozy-system-labeler
+  namespace: cozy-system
+  annotations:
+    helm.sh/hook: pre-install,pre-upgrade
+    helm.sh/hook-weight: "-100"
+    helm.sh/hook-delete-policy: before-hook-creation,hook-succeeded
+spec:
+  backoffLimit: 3
+  ttlSecondsAfterFinished: 60
+  template:
+    spec:
+      serviceAccountName: cozy-system-labeler
+      restartPolicy: OnFailure
+      containers:
+      - name: kubectl
+        image: alpine/k8s:1.32.0
+        imagePullPolicy: IfNotPresent
+        command:
+        - kubectl
+        - label
+        - --overwrite
+        - namespace
+        - cozy-system
+        - cozystack.io/system=true
+        - pod-security.kubernetes.io/enforce=privileged

packages/core/installer/templates/cozystack-operator.yaml

@@ -4,16 +4,6 @@
 {{- end -}}
 ---
 apiVersion: v1
-kind: Namespace
-metadata:
-  name: cozy-system
-  labels:
-    cozystack.io/system: "true"
-    pod-security.kubernetes.io/enforce: privileged
-  annotations:
-    helm.sh/resource-policy: keep
----
-apiVersion: v1
 kind: ServiceAccount
 metadata:
   name: cozystack