fix(e2e): align local docker_services_e2e with shared readiness helper

[mkostromin-sigma]

Summary

Follow-up to #1666 after the CI-first pre-start lands:

• Extract shared `wait_for_e2e_stack` (ordered probes + log dump)
• Local standalone path in `tests/e2e/conftest.py` uses the same helper (still may own up, but not a divergent wait)
• Dedupe `wait_for_server_readiness` in `tests/e2e/utils.py` into the shared helper

Blocked by the CI-first leaf under #1666.

[mkostromin-sigma]

Blocked by #1667 (CI-first leaf of #1666).