feat(infra): nightly DB-dump CronJobs feeding the Restic backup

pg_dumpall (all Postgres DBs + roles) and mongodump (all Mongo DBs) write
gzipped dumps to the hostPath /opt/dezky-backup/dumps at 02:50/02:52 UTC, which
the host Restic job (03:20) ships to the Storage Box. Each keeps the last 7
local dumps; Restic holds the real off-box retention.

- pods run as root (hostPath dir is root-owned, as is the host Restic reader)
- mongo job uses bash (mongo:7 /bin/sh is dash → no pipefail)
- creds from postgres-secret / mongo-secret via secretKeyRef

Verified: both jobs Complete, dumps present on the host
(postgres-all ~2.2MB w/ Authentik data, mongo archive).

infrastructure/production/fleet/data/db-backup.yaml

@@ -0,0 +1,106 @@
+# Nightly logical DB dumps -> hostPath /opt/dezky-backup/dumps, where the host
+# Restic job (03:20 UTC) picks them up and ships them to the Storage Box. These
+# run at 02:50/02:52 UTC so the dumps are fresh when Restic runs. Each keeps the
+# last 7 dumps locally (Restic keeps the real retention off-box).
+#
+# Pods run as root because the hostPath dir is root-owned (so the host Restic,
+# also root, can read the dumps). Single-node cluster; trusted backup job.
+---
+apiVersion: batch/v1
+kind: CronJob
+metadata:
+  name: postgres-backup
+  namespace: dezky-data
+spec:
+  schedule: "50 2 * * *"
+  concurrencyPolicy: Forbid
+  successfulJobsHistoryLimit: 3
+  failedJobsHistoryLimit: 3
+  jobTemplate:
+    spec:
+      backoffLimit: 1
+      template:
+        spec:
+          restartPolicy: Never
+          securityContext:
+            runAsUser: 0
+          containers:
+            - name: pgdump
+              image: postgres:16-alpine
+              command: ["/bin/sh", "-c"]
+              args:
+                - |
+                  set -euo pipefail
+                  ts=$(date +%Y%m%d-%H%M%S)
+                  out=/dump/postgres-all-$ts.sql.gz
+                  echo "pg_dumpall (all DBs + roles) -> $out"
+                  PGPASSWORD="$POSTGRES_PASSWORD" pg_dumpall -h postgres.dezky-data -U postgres | gzip > "$out"
+                  ls -1t /dump/postgres-all-*.sql.gz | tail -n +8 | xargs -r rm -f
+                  ls -la /dump/postgres-all-*.sql.gz | tail -3
+              env:
+                - name: POSTGRES_PASSWORD
+                  valueFrom:
+                    secretKeyRef:
+                      name: postgres-secret
+                      key: POSTGRES_PASSWORD
+              volumeMounts:
+                - name: dumps
+                  mountPath: /dump
+          volumes:
+            - name: dumps
+              hostPath:
+                path: /opt/dezky-backup/dumps
+                type: DirectoryOrCreate
+---
+apiVersion: batch/v1
+kind: CronJob
+metadata:
+  name: mongo-backup
+  namespace: dezky-data
+spec:
+  schedule: "52 2 * * *"
+  concurrencyPolicy: Forbid
+  successfulJobsHistoryLimit: 3
+  failedJobsHistoryLimit: 3
+  jobTemplate:
+    spec:
+      backoffLimit: 1
+      template:
+        spec:
+          restartPolicy: Never
+          securityContext:
+            runAsUser: 0
+          containers:
+            - name: mongodump
+              image: mongo:7
+              command: ["/bin/bash", "-c"]
+              args:
+                - |
+                  set -euo pipefail
+                  ts=$(date +%Y%m%d-%H%M%S)
+                  out=/dump/mongo-$ts.archive.gz
+                  echo "mongodump (all DBs) -> $out"
+                  mongodump --host mongo.dezky-data \
+                    --username "$MONGO_USER" --password "$MONGO_PASS" \
+                    --authenticationDatabase admin --archive --gzip > "$out"
+                  ls -1t /dump/mongo-*.archive.gz | tail -n +8 | xargs -r rm -f
+                  ls -la /dump/mongo-*.archive.gz | tail -3
+              env:
+                - name: MONGO_USER
+                  valueFrom:
+                    secretKeyRef:
+                      name: mongo-secret
+                      key: root-username
+                - name: MONGO_PASS
+                  valueFrom:
+                    secretKeyRef:
+                      name: mongo-secret
+                      key: root-password
+              volumeMounts:
+                - name: dumps
+                  mountPath: /dump
+          volumes:
+            - name: dumps
+              hostPath:
+                path: /opt/dezky-backup/dumps
+                type: DirectoryOrCreate