feat(BAT-005): add broker credential CLI command with persistence and tests

- Add CredentialService for managing broker credentials
- Implement credential CLI commands (create, list, get, update, delete)
- Add postgres repository support for credential operations
- Add comprehensive test coverage for credential CLI
- Update docs/batches/index.md and docs/srs/index.md with BAT-005
- Update docs/project-structure.md to reflect credential service

docs/srs/index.md

@@ -74,7 +74,7 @@
 
 ## Next Requirement ID
 
-- Current: `REQ-015`
+- Current: `REQ-016`
 - Rule: `Requirement Register`에 있는 가장 큰 REQ 번호보다 정확히 1 커야 한다.
 
 ## Requirement Register
@@ -95,9 +95,12 @@
 | REQ-012 | service-token rotate CLI 명령 구현 | Interface | Approved | Medium | repository-maintainers | [REQ-012](./Interface/req-012_service-token-rotate-cli.md) |
 | REQ-013 | CLI `portfolio list --user` 필수화 및 소유자 기반 조회 | Interface | Implemented | Medium | repository-maintainers | [REQ-013](./Interface/req-013_portfolio-list-user-required.md) |
 | REQ-014 | CLI `portfolio create --user` 필수화 및 소유자 설정 | Interface | Implemented | Medium | repository-maintainers | [REQ-014](./Interface/req-014_portfolio-create-user-required.md) |
+| REQ-015 | CLI `credential` 명령 그룹 구현 (브로커 인증 정보 관리) | Interface | Approved | Medium | repository-maintainers | [REQ-015](./Interface/req-015_broker-credential-cli.md) |
 
 ## Recent Change Log Summary
 
+- 2026-05-03: REQ-015 Approved 전환 — minor-change fast path (단일 저위험 REQ)
+- 2026-05-03: REQ-015 Proposed 생성 — CLI `credential` 명령 그룹 구현 (브로커 인증 정보 관리)
 - 2026-05-02: REQ-014 Implemented 전환 — BAT-004 verification evidence 확인 (44 passed)
 - 2026-05-02: REQ-014 Approved 직행 (minor-change) — CLI `portfolio create --user` 필수화 및 소유자 설정
 - 2026-05-02: REQ-013 Implemented 전환 — BAT-003 verification evidence 확인 (41 passed)