fix(test): wait for PostgreSQL TCP readiness

[rcyw]

Failure

Post-Merge Full source regression on main 69d71616ba8f78066786aacd241b840e916cd94c failed in controld-postgres-test: node enrollment E2E reached PostgreSQL while it was still starting (SQLSTATE 57P03). The script used pg_isready without a host, so the official image socket-only bootstrap server satisfied readiness before the final TCP server was available to the tests.

Fix

Probe final PostgreSQL TCP readiness in the control-plane integration runner and the directly related CLI E2E runner. Keep the CLI database existence query on the local socket to avoid passing a test password on a command line. The probe remains bounded and fails closed; no retries are added to application code or assertions relaxed.

Verification

• Original failing job: https://github.com/cofy-x/axern/actions/runs/35951653248/job/107481291821
• Official image entrypoint confirms bootstrap server uses empty listen_addresses.
• make controld-postgres-test with a fresh container passed, including TestNodeEnrollmentTLSPostgresE2E.
• make cli-e2e-environment-contract, shell syntax checks, git diff --check, and Forge make axern-cn-verify-changed passed.

Release Check for the older main SHA was canceled before final publication. v0.11.4 tags remain unused. After this fix merges, restart Release Check on the new exact main SHA; do not reuse the canceled candidate.