[Bug] Doris operator fails to create BE StatefulSet when feSpec.replicas=0

### Search before asking

- [x] I had searched in the [issues](https://github.com/apache/doris-operator/issues?q=is%3Aissue) and found no similar issues.

### Version

25.8.0

### What's Wrong?

When deploying a DorisCluster with feSpec.replicas: 0 and beSpec.replicas: 1 (intending to deploy only BE), the BE StatefulSet is not created. The operator expects an FE StatefulSet to exist for internal coordination.

### What You Expected?

BE StatefulSet should be created even when FE replicas=0

### How to Reproduce?

Deploy helm chart with:
```yalm
feSpec:
replicas: 0
beSpec:
replicas: 1
```

### Anything Else?

From the logs

fe controller controlClusterPhaseAndPreOperation get fe StatefulSet failed, err: StatefulSet.apps "test-doris-4-doris-be-fe" not found

I can look into submitting a PR, I haven't looked at the code yet but I do know Go

### Are you willing to submit PR?

- [x] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Start by tracing the FE controller's controlClusterPhaseAndPreOperation path mentioned in the log, then inspect how it handles a missing FE StatefulSet when feSpec.replicas is 0. Reproduce with the provided Helm values and verify that a BE StatefulSet is created with one replica despite zero FE replicas.

Scritto dal modello di indicizzazione a partire dal testo della issue.