Local Docker test runner: fix Phase 2/3/4 failures

Fix remaining failures in `scripts/test-local-docker.ps1`:\n- Phase 2: Zammad healthcheck timing (too aggressive)\n- Phase 3: FreePBX init time (bundled MariaDB needs full 3-5 min)\n- Phase 4: Graylog + Snipe-IT healthcheck tuning\nApply the same patterns proven in the Azure lab scripts (`; true` pipefail fix, retry loops, `/proc/net/tcp` port checks).