score/ts_client: Create AoU requirements

> [!IMPORTANT]
> Link the implementing PR to this issue by including `Closes #83` in the PR description or commit message.

### What

Write the Assumption of Use requirements for `score/ts_client`, capturing all preconditions that publisher and receiver users must fulfil.

`score/ts_client` provides a shared memory IPC channel between TimeSlave and TimeDaemon. Examples: the publisher must call `Connect()` before `Publish()`; the receiver must not read until the shared memory region has been created by the publisher; the SHM path configuration must match on both sides. Author as `aou_req` nodes at `score/ts_client/docs/requirements/ts_client_aou.rst`.

### Acceptance Criteria

- [ ] `score/ts_client/docs/requirements/ts_client_aou.rst` created
- [ ] All publisher-side and receiver-side preconditions captured as `aou_req` nodes with `:status: valid`
- [ ] Every `aou_req` links back to the relevant `comp_req` it restricts

### References

- [S-CORE Requirements Engineering](https://eclipse-score.github.io/process_description/main/process_areas/requirements_engineering/)