ADR Diffs

## Feature Proposal

### Target Project:
Calm Hub UI
Calm CLI (by extension, CALM Shared and CALM Models)

### Description of Feature:
This feature has two components
- The Calm Hub UI component which will allow seeing the diff between ADR revisions on a CALM Hub UI.
- The CALM CLI which will allow diffing between the `adrs` property on two different CALM JSONs.

### User Stories:
"As a developer, I want to run `calm adr-diff` between two architectures so that I can identify what ADR links have been added or removed."

"As a developer, I want to make at most three clicks on the CALM Hub UI to see the diff between two revisions of an ADR."

### Current Limitations:
It's just not been implemented yet.

### Proposed Implementation:
We can use the implementation of the diff command as an example for the CLI: https://github.com/finos/architecture-as-code/pull/2442

We can use the implementation of the diff view in Calm Hub UI as an example for the Calm Hub UI: https://github.com/finos/architecture-as-code/pull/2482

### Alternatives Considered:
Using the same ADR diff implementation on CALM CLI and CALM Hub UI - not possible because the first is a list of URL links while the second is a large string - both need to be treated differently.

### Testing Strategy:
Existing unit tests and integration tests, followed by user testing.

### Documentation Requirements:
Any documentation relevant to CLI or CALM Hub UI.

### Implementation Checklist:
- [x] Design reviewed and approved
- [ ] Implementation completed
- [ ] Tests written and passing
- [ ] Documentation updated
- [ ] Relevant workflows updated (if needed)
- [ ] Performance impact assessed

### Additional Context:
...add any other context, diagrams, mockups, or screenshots about the feature request here...