New example along storyline: Planned maintenance

### Description

As described in https://cwiki.apache.org/confluence/display/AIRFLOW/Examples+Refurbish

A new Dag is implemented along the described storyline for "Maintenance"

This includes:

- New Dag is added in Taskflow as well as classic implementation
- Dag is according to checklist
- Previous examples that are content-wise replaced are deleted to incrementally clean-up
- Airflow documentation is adjusted to point to new examples are replaced
- General example storyline overview is adjusted and the functioning of the new example is described

### Use case/motivation

Airflow Examples have been grown in number and focus over the past years. They purpose multiple things:

Serve as tutorials to learn Airflow DAG implementation
Serve with code snippets for documentation
Serve for testing the setup
(some) service for CI integration testing

Some example DAGs are in a good quality, some are not following best practices. Current examples do not follow a structure.

There are example DAGs contained in the Airflow core (currently pushed to standard provider/example_dags) as well as there are more examples in other providers. But examples from other providers are lot loaded automatically.

So in the [Airflow 3 Dev Calls](https://cwiki.apache.org/confluence/display/AIRFLOW/Airflow+3+Dev+call%3A+Meeting+Notes#Airflow3Devcall:MeetingNotes-22May2025) there was a demand named to clean-up and optimize example DAGs.

### Related issues

#52476 is made before and might be adjusted

### Are you willing to submit a PR?

- [ ] 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 the Examples Refurbish storyline and related issue #52476, then inspect the existing Taskflow and classic example DAGs. Implement the planned-maintenance example according to the checklist, remove examples it replaces, and update the referenced documentation and storyline overview so the new example is described and linked.

Written by the indexing model from the issue text.