Sync Frontend and APIserver docker variables

### Current Behavior

Deploying Dependency Track using the Frontend and APIserver via docker I need to set some variables twice with different names.
Due to [LegacyConfigPropertyValidator](https://github.com/DependencyTrack/dependency-track/blob/dc76b567c5f24e46139450aba1da968055d45252/apiserver/src/main/java/org/dependencytrack/common/LegacyConfigPropertyValidator.java#L45) docker deployment with a shared env file keeps boot-looping. The co-existance of the old ` OIDC_CLIENT_ID` and the new ` DT_OIDC_CLIENT_ID` since v5.x is the cause of this.

The Frontend still requires the old ` OIDC_CLIENT_ID` variable and it needs to be identical for both services anyway.

### Proposed Behavior

I propose a simple fix in the Frontend Repo.
A simple change in [docker/docker-entrypoint.d/30-oidc-configuration.sh](https://github.com/DependencyTrack/frontend/blob/48a7b37253b9145a95dee81133434fbb68f43264/docker/docker-entrypoint.d/30-oidc-configuration.sh) should migrate the Frontend to the new `DT_` prefixed variable names too.

I also suggest migrating ` OIDC_ISSUER` to `DT_OIDC_ISSUER` at the same time.

---

Please Note: it needs to be reflected **in the docs too**.
[rendered docs](https://dependencytrack.github.io/docs/next/guides/administration/configuring-oidc/) and [link to repo](https://github.com/DependencyTrack/docs/blob/main/docs/guides/administration/configuring-oidc.md). There's also a link to the "app properties" on that page that only show the new variable names. THIS actually caused a lot of trouble for me when deploying it.
[Rendered](https://dependencytrack.github.io/docs/next/reference/configuration/properties/#openid-connect) and [Repo Link](https://github.com/DependencyTrack/docs/blob/05a39c8c9738c8a90fed9d2a7f550cf99da53f22/docs/reference/configuration/properties.md?plain=1#L1509) for this too.

Summary: There's variables in the frontend and apiserver that could be the same name for easier docker deployment.
Benefit: Updating/Fixing the docs for this would've saved me about 1.5 hours today.

### Checklist

- [x] I have read and understand the [contributing guidelines](https://github.com/DependencyTrack/dependency-track/blob/main/CONTRIBUTING.md#filing-issues)
- [x] I have checked the [existing issues](https://github.com/DependencyTrack/dependency-track/issues) for whether this enhancement was already requested

Start with docker/docker-entrypoint.d/30-oidc-configuration.sh in the Frontend repository and trace how OIDC_CLIENT_ID and OIDC_ISSUER are read. Then update docs/guides/administration/configuring-oidc.md and docs/reference/configuration/properties.md; done means the frontend and API server use the DT_ variable names consistently and the documentation reflects them.

Written by the indexing model from the issue text.