feat(blog): add platform-managed backups introduction post (#566)

## Summary

- Add blog post "Platform-Managed Backups in Cozystack"
- Page bundle with 8 screenshots + 1200×630 social card (OG image)

## What

Introduction post covering the backup API: BackupJob, Plan, Backup,
RestoreJob, and BackupClass. Walks through tenant workflow (one-shot and
scheduled backups, in-place vs to-copy restore) and admin customization
of BackupClasses. Includes custom strategy extension points.

## Why

New feature needs blog coverage to drive awareness and provide a clear
getting-started reference for both tenant users and cluster admins.

## Preview

https://cozystack.io/blog/2026/05/platform-managed-backups-in-cozystack/

Author: tym83

content/en/blog/2026-05-31-platform-managed-backups-in-cozystack/1.png

@@ -0,0 +1,124 @@
+---
+title: "Platform-Managed Backups in Cozystack"
+slug: platform-managed-backups-in-cozystack
+date: 2026-05-31
+author: "Timur Tukaev"
+description: "Cozystack introduces platform-managed backups: tenants declare what to protect, the platform handles where and how. One-shot jobs, scheduled plans, and point-in-time restore for Postgres, MariaDB, ClickHouse, and KubeVirt VMs."
+images:
+  - "social-card.png"
+article_types:
+  - how-to
+topics:
+  - platform
+  - backup
+---
+
+Backups are everyone's responsibility and, too often, nobody's job. On a multi-tenant platform the problem is sharper: tenants want to protect their own databases and VMs, but they shouldn't be handed S3 credentials or asked to wire up storage. Cozystack closes that gap with **platform-managed backups** — a clear API where tenants declare **what** to protect and the platform takes care of **where** and **how**.
+
+## The model in one minute
+
+There are five objects, split cleanly between two audiences.
+
+Tenant-facing:
+
+- **BackupJob** — a one-off backup.
+- **Plan** — scheduled (cron) backups.
+- **Backup** — represents the artifact produced by a BackupJob.
+- **RestoreJob** — restores a backup into a target application.
+
+{{< figure src="1.png" alt="Diagram of the five backup API objects and their relationships" width="720" >}}
+
+Admin-owned:
+
+- **BackupClass** — binds an application Kind to a backup strategy and storage, and tunes desired parameters.
+
+Tenants reference a `BackupClass` by name and never see S3 endpoints, credentials, paths, or underlying resources — those are accessible to cluster administrators only. The platform performs backups in a managed way and guarantees robustness and stability.
+
+Cozystack ships a predefined class `cozy-default` and a storage bucket `cozy-backups` — no configuration needed to get started.
+
+{{< figure src="2.png" alt="BackupClass object showing the admin-controlled binding between application Kind, strategy, and storage" width="720" >}}
+
+## For tenant users: back up and restore your apps
+
+The `cozy-default` BackupClass is provisioned automatically and already covers Postgres, MariaDB, ClickHouse, Etcd, and KubeVirt VMs (`VMInstance`, `VMDisk`). You only need to select your application — no configuration or storage setup required.
+
+{{< figure src="3.png" alt="Cozystack dashboard showing the BackupJob creation form for a Postgres application" width="720" >}}
+
+{{< figure src="4.png" alt="BackupJob status showing phase Succeeded with backup artifact details" width="720" >}}
+
+We recommend starting with a one-shot `BackupJob` to verify correct operation before setting up a scheduled Plan.
+
+```yaml
+apiVersion: backups.cozystack.io/v1alpha1
+kind: BackupJob
+metadata:
+  name: oneshot-mariadb
+  namespace: tenant-user1
+spec:
+  applicationRef:
+    apiGroup: apps.cozystack.io
+    kind: MariaDB
+    name: mariadbinstance
+  backupClassName: cozy-default
+```
+
+Use `Plan` for recurring backups:
+
+{{< figure src="5.png" alt="Cozystack dashboard showing the Plan creation form with cron schedule configuration" width="720" >}}
+
+{{< figure src="6.png" alt="Plan list view showing active scheduled backup plans and their last run status" width="720" >}}
+
+```yaml
+apiVersion: backups.cozystack.io/v1alpha1
+kind: Plan
+metadata:
+  name: maria-nightly-backups
+  namespace: tenant-user1
+spec:
+  applicationRef:
+    apiGroup: apps.cozystack.io
+    kind: MariaDB
+    name: mariadbinstance
+  backupClassName: cozy-default
+  schedule:
+    type: cron
+    cron: "0 2 * * *"  # at 02:00
+```
+
+Once a BackupJob reaches `phase: Succeeded`, you can restore from it:
+
+{{< figure src="7.png" alt="RestoreJob creation form with source backup and target application configured" width="720" >}}
+
+Restoring comes in two flavors. A `RestoreJob` either replays into the same application (**in-place** — fast rollback, but destructive) or into a freshly provisioned copy of the same Kind (**to-copy** — safe for DR drills and validation). You choose by whether you set `targetApplicationRef`.
+
+## For cluster admins: defaults, tuning, and opt-ins
+
+For most platforms, `cozy-default` ships ready and your tenants can back up immediately without any setup.
+
+{{< figure src="8.png" alt="BackupClass manifest showing strategy, storage binding, and retention configuration" width="720" >}}
+
+Reach for a custom `BackupClass` when you need to:
+
+- **tune retention** for a specific application or tenant;
+- **enable a new Kind** not bound by default;
+- **use a dedicated bucket** — split storage for simplified maintenance.
+
+## Going further: custom strategies
+
+The backups API is extensible. If a driver you need doesn't exist yet, you have two routes:
+
+- **No code:** the generic Job-based strategy. Reuse a plain Kubernetes Job as the backup mechanism — useful for bespoke or self-managed workloads. See the [NATS example](https://github.com/cozystack/cozystack/blob/main/examples/backups/nats/01-create-strategy.sh).
+- **A custom strategy controller** built against the backups API and embedded in Cozystack, for first-class lifecycle handling.
+
+## Learn more
+
+- [Application Backup and Recovery](https://cozystack.io/docs/v1.4/applications/backup-and-recovery/)
+- [Backup Classes — admin guide](https://cozystack.io/docs/v1.4/operations/services/backup-classes/)
+- [More examples](https://github.com/cozystack/cozystack/tree/main/examples/backups)
+
+## Join the community
+
+- [GitHub](https://github.com/cozystack/cozystack)
+- Telegram [group](https://t.me/cozystack)
+- Slack [group](https://kubernetes.slack.com/archives/C06L3CPRVN1) (get invite at [https://slack.kubernetes.io](https://slack.kubernetes.io))
+- [Community Meeting Calendar](https://calendar.google.com/calendar?cid=ZTQzZDIxZTVjOWI0NWE5NWYyOGM1ZDY0OWMyY2IxZTFmNDMzZTJlNjUzYjU2ZGJiZGE3NGNhMzA2ZjBkMGY2OEBncm91cC5jYWxlbmRhci5nb29nbGUuY29t)