Use Kubernetes-recommended labels for airflow helm chart

### Description

Kubernetes offers a [list of recommended labels](https://kubernetes.io/docs/concepts/overview/working-with-objects/common-labels/#labels) for grouping resource objects. The prefix app.kubernetes.io differentiates these recommended labels from custom labels.

Why is it needed?
Enhancing readability and maintainability

References
https://helm.sh/docs/chart_best_practices/labels/#standard-labels
https://kubernetes.io/docs/concepts/overview/working-with-objects/common-labels/#labels

### Use case/motivation

https://github.com/apache/airflow/blob/913eff6759bf89d635ef1df1a0db23c157e48c4b/chart/templates/webserver/webserver-deployment.yaml#L36-L40

The above labels would be changed as follows:

```yaml
app.kubernetes.io/part-of: airflow
app.kubernetes.io/component: webserver
app.kubernetes.io/instance: {{ .Release.Name }}
helm.sh/chart: {{ .Chart.Name }}-{{ .Chart.Version | replace "+" "_" }}
app.kubernetes.io/managed-by: {{ .Release.Service }}
```

### Related issues

_No response_

### Are you willing to submit a 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://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

Start with chart/templates/webserver/webserver-deployment.yaml at the referenced labels, then inspect the other Airflow Helm chart templates to determine whether the same convention is needed across resources. Compare the rendered labels with the Kubernetes and Helm standard-label references; done means the chart uses the recommended labels consistently without breaking existing chart behavior.

Written by the indexing model from the issue text.