Support workload identity federation as alternative to API keys

### Current Behavior

Currently, non-human clients must authenticate via long-lived API keys. This is both risky (leaked keys stay valid until manually revoked), and cumbersome (manual minting, distribution, rotation).

The industry is converging on tackling this problem using [workload identity federation](https://nhimg.org/glossary/workload-identity-federation/) (WIF):

> Workload identity federation is the practice of letting a workload prove who it is in one trust domain and receive a short-lived credential in another, without storing a long-lived password, API key, or shared secret. In NHI operations, that makes it a control pattern for reducing credential sprawl across cloud, Kubernetes, CI/CD, and hybrid environments.

Some high-assurance environments are actively banning use of long-lived credentials and require tedious exception processes if WIF is not available.

### Proposed Behavior

We should support WIF to make it easier and more secure to integrate with us.

> [!WARNING]
> Requires service accounts (#7055) to be implemented first.

References:

* https://nhimg.org/glossary/workload-identity-federation/
* https://developers.openai.com/api/docs/guides/workload-identity-federation
* https://platform.claude.com/docs/en/manage-claude/workload-identity-federation
* https://docs.snowflake.com/en/user-guide/workload-identity-federation

### 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

No files, tests, or implementation entry points are named. Start by reading the service-account prerequisite in issue #7055 and the linked WIF documentation, then trace the existing API-key authentication flow. Done means non-human clients can use short-lived federated credentials instead of long-lived API keys.

Written by the indexing model from the issue text.