Improvement: Add system integration tests for the PTP time-synchronization pipeline (Linux/Docker + QNX/QEMU)

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Purpose
- Deliver a system-level, end-to-end PoC verification campaign for `score_time` that exercise the full PTP time-synchronization pipeline end-to-end on Linux/Docker + QNX/QEMU platforms.

Scope
The system tests launch real `time_slave` + `time_daemon` processes plus a PTP master and an example app, all running inside a single OS environment, and assert that time synchronization converges correctly across the whole stack. Two environments are targeted:

- **Case 1 — Linux (Ubuntu 24.04) via Docker container**.
- **Case 2 — QNX 8 via QEMU (x86_64)**:

Deliverables
- proposes to adopt ITF for `score_time` in order to stay aligned with SCORE testing standards.
- provides a generic ITF supporting both Docker and QEMU backends
- End-to-end convergence when a genuine PTP master is present
- Process lifecycle: startup ordering, crash/restart behaviour, shared-memory lifetime across process boundaries

Acceptance criteria
- Test specification and implementation exist. Test passes.