[Feat]: Ability to customize service name per container/port

### What feature?

I'd like to have the ability to rename/customize the _service name_ that is given to a particular container/port combination.

For example a docker-compose file like this:
```
services:
service-a:
ports:
- 8080:8080
- 8081:8081
```

Gives two urls:
```
https://service-a-ui-8080--.livecycle.run/
https://service-a-ui-8081--.livecycle.run/
```

I'd like the ability to override the urls to anything I would like: i.e.
```
# for service-a 8080
https://api--.livecycle.run/

# for service-a 8081
https://metrics--.livecycle.run/
```

Ideally, this would still work with the service discovery and PREEVY_BASE_URL documented [here](https://preevy.dev/recipes/service-discovery#example)

### Describe the solution you'd like

The existing `preevy.expose` label could be augmented to support an optional prefix of `name=`

Example:
```
preevy.expose: api=8080,metrics=8081
```

The only downside I can think of is if you might have multiple containers that would define a specific url, and this would have to be caught and have an error thrown (i.e. if two containers specified an `api` port to expose). This is an example of an invalid config:

```
services:
service-a:
ports:
- 8080:8080
labels:
preevy.expose: api=8080
service-b:
ports:
- 7777:7777
labels:
# both containers use api, this would be invalid
preevy.expose: api=7777
```

### Describe alternatives you've considered

- Currently the only way I can think of doing this is to rename my containers

### Additional context

See https://livecyclecommunity.slack.com/archives/C05S50C9Z5F/p1707144759493989

### Add screenshots

_No response_

### Record

- [X] I agree to follow this project's Code of Conduct

Start by tracing how the existing preevy.expose label is parsed and how service discovery and PREEVY_BASE_URL derive exposed URLs. Implement the optional name=port syntax, ensure duplicate names are rejected, and verify that customized URLs still work with service discovery.

Written by the indexing model from the issue text.