fix(server): pin resolved advertise address

[zhikunyao]

Summary

• retain the IP returned by the existing advertise-hostname readiness check
• pass the stable IP to memberlist instead of resolving the hostname a second time
• add a regression test covering hostname-to-IP pinning before node startup

Root cause

waitAndStartCurrentNode waited until the configured gossip advertise hostname resolved, but discarded the resolved IP. membership.NewServerNode then performed another DNS lookup. During Kubernetes Headless Service propagation, that second lookup could fail after the readiness lookup had succeeded, leaving a partially initialized memberlist listener and causing subsequent retries to report address already in use.

Test plan

• go test -race -short ./server ./common/net ./common/membership -count=1
• go test -run '^$' ./...
• gofmt -d server/service.go server/service_test.go
• git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.59%. Comparing base (e99c5e6) to head (8e19423).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #251      +/-   ##
==========================================
- Coverage   83.62%   83.59%   -0.04%     
==========================================
  Files         182      182              
  Lines       25452    25453       +1     
==========================================
- Hits        21285    21277       -8     
- Misses       3189     3193       +4     
- Partials      978      983       +5     

Components	Coverage Δ
Server	83.07% <100.00%> (+<0.01%)	⬆️
Client	90.42% <ø> (-0.13%)	⬇️
Meta	86.99% <ø> (ø)
Common	88.70% <ø> (-0.04%)	⬇️

Files with missing lines	Coverage Δ
server/service.go	79.39% <100.00%> (+0.02%)	⬆️

... and 6 files with indirect coverage changes

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[github-actions]

❌ E2E Service failed. Comment /rerun-e2e-service to rerun, or /rerun to rerun all failed checks.

[github-actions]

❌ Component Integration Test failed. Comment /rerun-component-test to rerun, or /rerun to rerun all failed checks.