Add recommendation pages for all DBs

docs/guides/cassandra/recommendation/_index.md

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+---
+title: Cassandra Recommendation
+menu:
+  docs_{{ .version }}:
+    identifier: cassandra-recommendation
+    name: Recommendation
+    parent: cas-cassandra-guides
+    weight: 100
+menu_name: docs_{{ .version }}
+---

docs/guides/cassandra/recommendation/recommendation.md

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+---
+title: Cassandra Recommendation Overview
+menu:
+  docs_{{ .version }}:
+    identifier: cassandra-recommendation-overview
+    name: Recommendation Overview
+    parent: cassandra-recommendation
+    weight: 10
+menu_name: docs_{{ .version }}
+section_menu_id: guides
+---
+
+> New to KubeDB? Please start [here](/docs/README.md).
+
+# Cassandra Recommendation
+
+## Overview
+
+A `Recommendation` is a Kubernetes-native CRD created by the **KubeDB Ops-Manager** and reconciled by the **KubeDB Supervisor**. For a Cassandra instance managed by KubeDB, the Ops-Manager watches the database's state and emits a Recommendation whenever it detects an action you should take — a newer version, an expiring TLS certificate, or an authentication secret nearing its rotation deadline.
+
+Nothing runs until the Recommendation is approved — either by you (`status.approvalStatus: Approved`) or automatically through an `ApprovalPolicy` bound to a `MaintenanceWindow`. Once approved, the Supervisor creates the corresponding `CassandraOpsRequest` and tracks it to completion.
+
+This page is the **Cassandra-specific intro**: which recommendations apply to Cassandra and which spec fields trigger them. For prerequisites, Helm flags that control generation timing, and the full Recommendation lifecycle, see:
+
+- [Recommendation Configuration](/docs/operatormanual/recommendation/configuration.md) — prerequisites, Supervisor CRD install, and all Helm flags.
+- [Recommendation Overview](/docs/operatormanual/recommendation) — architecture and lifecycle walkthrough.
+
+<p align="center">
+  <img alt="Recommendation Lifecycle" src="/docs/operatormanual/recommendation/images/recommendation-generation.png">
+</p>
+
+---
+
+## Relevant KubeDB concepts
+
+- [CassandraOpsRequest](/docs/guides/cassandra/concepts/cassandraopsrequest.md)
+- [CassandraRotateAuth](/docs/guides/cassandra/rotate-auth/overview.md)
+- [CassandraReconfigureTLS](/docs/guides/cassandra/tls/overview.md)
+- [CassandraUpdateVersion](/docs/guides/cassandra/update-version/overview.md)
+
+---
+
+## Recommendation types for Cassandra
+
+| Type                              | Triggered when                                                                    | Walkthrough                                                                                                  |
+| --------------------------------- | --------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ |
+| **Version Update**                | A newer major, minor, or patch version becomes available                          | [Version Update Recommendation](/docs/operatormanual/recommendation/version-update-recommendation.md)        |
+| **Same-Version Update**           | The container image for your *current* version is refreshed (e.g. security patch) | [Version Update Recommendation](/docs/operatormanual/recommendation/version-update-recommendation.md)        |
+| **TLS Certificate Rotation**      | An issued certificate is approaching its expiry threshold                         | [TLS Certificate Rotation Recommendation](/docs/operatormanual/recommendation/rotate-tls-recommendation.md)  |
+| **Authentication Secret Rotation** | The auth secret is approaching its `rotateAfter` deadline                         | [Authentication Secret Rotation Recommendation](/docs/operatormanual/recommendation/rotate-auth-recommendation.md) |
+
+---
+
+## Triggers specific to Cassandra
+
+This section shows the minimal Cassandra CR fields that cause each recommendation to be generated. For deeper, end-to-end walkthroughs use the links in the table above.
+
+### Authentication Secret Rotation
+
+```yaml
+apiVersion: kubedb.com/v1alpha2
+kind: Cassandra
+metadata:
+  name: cassandra-recommendation
+  namespace: demo
+spec:
+  version: "5.0.3"
+  authSecret:
+    kind: Secret
+    name: cassandra-auth
+    rotateAfter: 1h
+```
+
+In this configuration:
+
+* The `rotateAfter` field defines how long the authentication secret remains valid
+
+KubeDB monitors the configured lifecycle and generates a RotateAuth Recommendation based on the following conditions:
+
+* If the secret lifespan is greater than one month, a recommendation is generated when less than one month of validity remains
+
+* If the secret lifespan is less than one month, a recommendation is generated when approximately one-third of its validity remains
+
+Once approved, KubeDB creates an opsrequest to rotate the credentials automatically, ensuring:
+
+* No expired credentials
+
+* Improved security posture
+
+* Reduced manual intervention
+
+### TLS Certificate Rotation
+
+```yaml
+apiVersion: kubedb.com/v1alpha2
+kind: Cassandra
+metadata:
+  name: cassandra-recommendation
+  namespace: demo
+spec:
+  version: "5.0.3"
+  tls:
+    issuerRef:
+      apiGroup: cert-manager.io
+      kind: Issuer
+      name: cassandra-ca-issuer
+    certificates:
+      - alias: client
+        duration: 1h20m
+      - alias: server
+        duration: 2h10m
+```
+
+In this configuration:
+
+* The `spec.tls.certificates.duration` field defines how long each certificate remains valid
+
+KubeDB monitors the configured lifecycle and generates a RotateTLS Recommendation based on the following conditions:
+
+* If the certificate duration is greater than one month, a recommendation is generated when less than one month of validity remains
+
+* If the certificate duration is less than one month, a recommendation is generated when approximately one-third of its validity remains
+
+Once approved, KubeDB creates an opsrequest to reconfigure TLS automatically, ensuring:
+
+* Continuous secure communication
+
+* No unexpected certificate expiry
+
+* Seamless certificate renewal
+
+### Version Update
+
+```yaml
+apiVersion: kubedb.com/v1alpha2
+kind: Cassandra
+metadata:
+  name: cassandra-recommendation
+  namespace: demo
+spec:
+  version: "5.0.3"
+```
+
+In this configuration:
+
+* KubeDB monitors the running version of the database
+
+KubeDB monitors the configured lifecycle and generates a VersionUpdate Recommendation based on the following conditions:
+
+* If a newer container image is available for the current version, a recommendation is generated
+
+* If a patch version is released, a recommendation is generated
+
+* If a newer minor or major version becomes available, a recommendation is generated
+
+* If changes are introduced in the existing version image (e.g., security fixes or image updates without a version bump), a recommendation is generated
+
+For example: Recommending version update from `5.0.3` to `5.0.7`
+
+Once approved, KubeDB creates an opsrequest to perform the version upgrade automatically, ensuring:
+
+* Timely adoption of security patches and fixes
+
+* Access to new features and improvements
+
+* Consistent performance and stability across deployments
+
+### Same-Version Update
+
+```yaml
+apiVersion: kubedb.com/v1alpha2
+kind: Cassandra
+metadata:
+  name: cassandra-recommendation
+  namespace: demo
+spec:
+  version: "5.0.3"
+```
+
+In this configuration:
+
+* KubeDB monitors the container image of the current database version
+
+KubeDB monitors the configured lifecycle and generates a SameVersionUpdate Recommendation based on the following conditions:
+
+* If the container image backing the current version is updated (e.g., security patches or rebuilds without a version change), a recommendation is generated
+
+Once approved, KubeDB creates an opsrequest to update the running workload automatically, ensuring:
+
+* Security patches are applied without requiring a version upgrade
+
+* Consistency with the latest available container image
+
+* Improved reliability and maintainability
+
+---
+
+For prerequisites, Helm configuration flags, and the full cross-database Recommendation lifecycle, see the [Recommendation Configuration](/docs/operatormanual/recommendation/configuration.md) and [Recommendation Overview](/docs/operatormanual/recommendation) in the operator manual.

docs/guides/clickhouse/recommendation/_index.md

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+---
+title: ClickHouse Recommendation
+menu:
+  docs_{{ .version }}:
+    identifier: clickhouse-recommendation
+    name: Recommendation
+    parent: ch-clickhouse-guides
+    weight: 100
+menu_name: docs_{{ .version }}
+---