fix: include organization member roles

[zhangyangyu]

Description

Adds membership role and state fields to organization member list responses so clients can render admin/member state without separate membership lookups. The service now returns active membership metadata with listed users while preserving the distinct invitation role vocabulary used by pending invitations.

Tracking

N/A

Tests

• make check
• go test ./internal/rest -run TestOrganizationMemberHandlers -v
• go test ./internal/service

SSOT Drift Prevention Checklist

• Checked that this PR does not violate boundaries in docs/architecture.md or docs/module-contracts.md
• Package structure and dependencies are unchanged; no SSOT doc update needed
• Test conventions and coverage expectations are unchanged; no docs/test-strategy.md update needed
• CI, smoke, regression, and packaging workflows are unchanged; no docs/ci.md update needed