score/time: Create detailed design (comp_dd_sta)

> [!IMPORTANT]
> Link the implementing PR to this issue by including `Closes #86` in the PR description or commit message.

### What

Write the detailed design document for `score/time`.

Create `score/time/docs/detailed_design/index.rst` using the sphinx-needs `comp_dd_sta` directive. The detailed design decomposes the component into individual units, documents their internal responsibilities and interfaces, and connects every unit to requirements (`:implements:`) and architecture (`:satisfies:`). Source code must then reference this design via `// # req-Id:` comments.

Units to cover: `Clock` template + specialisations, `ClockSnapshot`, `ClockStatus` value types, `VehicleClockBackend` interface + `VehicleClockBackendImpl`, `ScopedClockOverride`, `ClockTestFactory`, domain mock classes; how `Clock` delegates to `VehicleClockBackend`; `:implements:` → `comp_req__time__*`, `:satisfies:` → `comp_arc_sta__time__*`.

### Acceptance Criteria

- [ ] `comp_dd_sta` directive in place with `:status: valid`
- [ ] All public units visible in static view
- [ ] `:implements:` and `:satisfies:` links present for every unit
- [ ] `req-Id` traceability comments in source for every traced unit

### References

- [S-CORE Implementation & Detailed Design](https://eclipse-score.github.io/process_description/main/process_areas/implementation/)