feat(etcd): weekly defrag CronJob to stay under the etcd backend quota

etcd's 2 GiB quota was reached on 2026-10-07 (backend 2.1 GiB, ~73 days of
churn). etcd raised NOSPACE and refused all writes, so kubelets could not post
node status: three nodes went NotReady and the tunnel origin pods on them
disappeared. Recovery was compact + defrag + alarm disarm per member.

The apiserver compacts every 5m, but compaction never shrinks the backend file -
only a defrag returns space, and nothing scheduled it. This adds:

- CronJob etcd-defrag (kube-system, Sundays 03:00): compact to the current
  revision, defrag each member sequentially, disarm NOSPACE, print before/after.
- Secret etcd-defrag-creds (SOPS/ksops, k8s/argocd/secrets): etcd CA plus a
  CN=etcd-defrag client cert signed by the cluster's etcd CA (expires 2036-10).

Applied by the existing apps: cluster-maintenance (directory) and 00-secrets
(ksops generator).

k8s/argocd/secrets/etcd-defrag-creds.enc.yaml

@@ -0,0 +1,27 @@
+apiVersion: v1
+kind: Secret
+metadata:
+    name: etcd-defrag-creds
+    namespace: kube-system
+    labels:
+        app.kubernetes.io/name: etcd-defrag
+type: Opaque
+stringData:
+    ca.crt: ENC[AES256_GCM,data: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,iv:KnW9LYNzxZ6r3Q6LTeOrgSLLPgiJlibVp6YmTEKBkjE=,tag:KTL1nOWdNWDA4dLVaA4//g==,type:str]
+    client.crt: ENC[AES256_GCM,data:IEmZe505SwkW3U5vmRtFxR6PpuSFGWEHflUZwyhSODzYG1zLM8olVWDtH+yUVI54kLXxTtcpMkKrTBjpAxHG8zUTLPdTCVzPMq6U20jH4PYFMzoldnSgpRl/eiADUmE4I32CBbPdM5nkPvjVEYMmRafEGyJctjG6Shhh/sUO1yE9A+h1R7o3UCRPttWTozSKN4dPi75v1TSAOLyXqvQYl5Ea9iKW47ea7Q+XTcoKfMPXsTJp44kiZnVW0VT/7xNydR7AVWJJzYltY5380j0Ho+7PfNd+QqmdodkaZPS4b0PaoinMiZ40JnChGVhdS91j3IkUlU1g/+G2iVnPR9KB07xqRubqiASxIvpSaSCeYl3rR7+dXYX18VpWcWnJ6XoREoqxJiqmMQWYSROYDTd4G/zs4Usuh5r0wIodmCjud+g89mmXFtH0PbsMCVvZDUswjVfeT2PUBm036TXlxF/1aAy2GDqycbPgJgDLyw9tdiQUZe2iA+Z/Wx80qgQjmmqCaw77cDergLFj9KnByl3Tinwfm+IWFeQiDW+fwSzz+/vrpl55BkSVkVhw7r2Jd6zyg4VtLVXbxYhzdNz695N+fjkZHuPE5tCwr4WCzAg3vSS9hA7IHo8k93WO8s6+KlyjuwTdjPIYZghebO4ktwdqvhvuqxv8Nzwpc5J7Z2H2IChjXg==,iv:l8BwxxEfHfYrm+mM5UE6Yj42DeeU9y23jjIE1KjIiME=,tag:HwRT6/myIsxc84BYDj3K6w==,type:str]
+    client.key: ENC[AES256_GCM,data:QD/Glf3lFslBEdEoJ3CNrYzlw2HLCvGSeVuJLtxnFne2aJOuw0sk/e0h/kSAxvG4dZ+LIWJLLbqTjKHOAhkvS/ZOA7GSea4ubNkvTkw8+JBRuYwb2D2iB8kZhlER/CpiGkYJukjkgGP1CzHdvBY1M88pW9w6rH74MD3jY47qExIaNduQj5vkUQZ8ajqkd79l0nk98ZTawfPG4AFcEtAIKAPIuubT2GZ3qqNLjOI7agbtRv8xI44hhb2wj5J9xdl1GrbOWwG5EOo+hLNrcAAOCcWBpNTUCKBy7mrk2ID8jX3HsFWN76DDlQzkhcphMhlM7g==,iv:49HGJAEgllEkB3YSiZLmbWs/vlbFbY52kiKesdGVC/Y=,tag:g8YZ9at3V2l6RFRfvO2lAQ==,type:str]
+sops:
+    age:
+        - enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSB4Z0h0R2dhbDdRcFJydE9o
+            R0hWeCtwVzluZWZlR0VtOXcxdW9FbklOQXlzCmo3eXNyNlFjejNETkJiVVRVWFhr
+            a2pORnhIQTI0UUk2N3dWMDZJcEhYU1UKLS0tIEduaHlmMHQza1A0TGVZb0JrbTYz
+            MWJwQjcrdkkzQXhOTmhycERsM0FtNVEKG+gBRcvUsyfRzuW999EQNzyDh2/5fY6p
+            8ab2xvTOJPiMUBTBuQZsA+iDImytUO/02ROQsbEZkALijp1nqrsV/g==
+            -----END AGE ENCRYPTED FILE-----
+          recipient: age1e5fq3hwxy78psus2nfvmtmua36g0u3suk78ephw6246l974d2utsvn0hla
+    encrypted_regex: ^(data|stringData)$
+    lastmodified: "2026-10-07T05:37:26Z"
+    mac: ENC[AES256_GCM,data:vu6ltV0jYQNGV4eqIcqAp9p2TJ8ULBX5JBELUgm/nA9GX+I6Pv3fyjpcHRSWY0HbLvCwgXd22CG4IYcj4HJFtQGZR7OcQA5WM5plZH3RCPdvPNix/798vkETfpJxorQjlHoq4nlr3dEmUCbzdtE07qV2W1M6GJr4C9xKvB947bQ=,iv:aA9mjZCFAoLEhGqkl6NfyBZ3x3vWGfLYYAEe8jXuA4U=,tag:Drdiji33ckDd8ildpvSEXw==,type:str]
+    version: 3.13.2

k8s/argocd/secrets/secret-generator.yaml

@@ -34,3 +34,4 @@ files:
   - forgejo-smtp-secrets.enc.yaml
   - paperless-ai-secrets.enc.yaml
     - pi-sandbox-secrets.enc.yaml
+    - etcd-defrag-creds.enc.yaml

k8s/infra/cluster-maintenance/etcd-defrag-cronjob.yaml

@@ -0,0 +1,101 @@
+# etcd defrag maintenance.
+#
+# Why this exists: the apiserver compacts etcd every 5m, but compaction only marks
+# superseded revisions free INSIDE the backend file -- the file never shrinks.
+# Only `etcdctl defrag` returns space to the filesystem, and nothing runs it
+# automatically. On 2026-10-07 the 2 GiB quota was reached after ~73 days
+# (backend 2.1 GiB) -> etcd raised the NOSPACE alarm -> etcd refused ALL writes
+# -> kubelets could not post node status -> 3 nodes went NotReady and the tunnel
+# origin pods on them vanished (502s). Recovery = compact + defrag + alarm disarm.
+#
+# This CronJob keeps the backend well under quota: compact to the current
+# revision, defrag each member sequentially, then disarm any NOSPACE alarm.
+#
+# Companion alerts (monitoring): etcd_mvcc_db_total_size_in_bytes /
+# etcd_server_quota_in_bytes > 0.8, and a NOSPACE alarm alert.
+#
+# Credentials: secret etcd-defrag-creds (kube-system), SOPS-managed in
+# k8s/argocd/secrets/etcd-defrag-creds.enc.yaml. Its client cert is signed by the
+# cluster's etcd CA and expires 2036-10 -- rotate it before then by re-running the
+# mint + re-encrypt (see the repo's sops workflow).
+apiVersion: batch/v1
+kind: CronJob
+metadata:
+  name: etcd-defrag
+  namespace: kube-system
+  labels:
+    app.kubernetes.io/name: etcd-defrag
+    app.kubernetes.io/part-of: cluster-maintenance
+spec:
+  schedule: "0 3 * * 0"            # Sundays 03:00, low traffic
+  concurrencyPolicy: Forbid
+  startingDeadlineSeconds: 600
+  successfulJobsHistoryLimit: 3
+  failedJobsHistoryLimit: 3
+  jobTemplate:
+    spec:
+      backoffLimit: 2
+      template:
+        spec:
+          restartPolicy: OnFailure
+          tolerations:
+            - key: node-role.kubernetes.io/control-plane
+              operator: Exists
+              effect: NoSchedule
+          containers:
+            - name: defrag
+              image: quay.io/coreos/etcd:v3.5.17
+              env:
+                - name: ETCDCTL_API
+                  value: "3"
+                - name: ETCDCTL_CACERT
+                  value: /etc/etcd/ca.crt
+                - name: ETCDCTL_CERT
+                  value: /etc/etcd/client.crt
+                - name: ETCDCTL_KEY
+                  value: /etc/etcd/client.key
+                - name: EPS
+                  value: "https://192.168.1.166:2379 https://192.168.1.214:2379 https://192.168.1.162:2379"
+              command: ["/bin/sh", "-c"]
+              args:
+                - |
+                  set -u
+                  PRIMARY=${EPS%% *}
+                  echo "== before =="
+                  etcdctl --endpoints=$EPS endpoint status -w table || true
+
+                  REV=$(etcdctl --endpoints=$PRIMARY endpoint status -w json \
+                        | sed -n 's/.*"revision":\([0-9]*\).*/\1/p' | head -1)
+                  if [ -n "$REV" ]; then
+                    echo "== compact to revision $REV =="
+                    etcdctl --endpoints=$PRIMARY compact "$REV" || true
+                  fi
+
+                  echo "== defrag each member (sequential, one at a time) =="
+                  rc=0
+                  for ep in $EPS; do
+                    echo "-- $ep"
+                    etcdctl --endpoints="$ep" defrag || { echo "DEFRAG-FAILED $ep"; rc=1; }
+                  done
+
+                  echo "== disarm NOSPACE =="
+                  for ep in $EPS; do
+                    etcdctl --endpoints="$ep" alarm disarm 2>/dev/null || true
+                  done
+
+                  echo "== after =="
+                  etcdctl --endpoints=$EPS endpoint status -w table || true
+                  etcdctl --endpoints=$PRIMARY alarm list || true
+                  exit $rc
+              resources:
+                requests: { cpu: 10m, memory: 32Mi }
+                limits:   { cpu: 200m, memory: 128Mi }
+              volumeMounts:
+                - name: creds
+                  mountPath: /etc/etcd
+                  readOnly: true
+          volumes:
+            - name: creds
+              secret:
+                secretName: etcd-defrag-creds
+                defaultMode: 0444