feat: connect portal portfolio and asset operations

[0xMuang]

Summary

• journal completed RFQ purchases exactly once and derive investor portfolio/history from the same state
• reflect investor purchases in issuer metrics
• add issuer ABCF pause/resume with confirmation, audit history and investor quote/fill blocking
• migrate the existing browser demo state without touching external wallet/RPC/operator boundaries

Verification

• npm test --prefix services/product-portal-demo
• JavaScript syntax checks and git diff --check
• headless Chrome: 18 assertions across buy, holdings, history, issuer metrics, pause, blocked order and resume

Stack

Depends on #92. Base is the portal feature branch; do not merge directly to main before #92.

[0xMuang]

이 포털은 production main 기능이 아니라 발표용 데모로 유지하기로 결정했습니다. #92 위에 쌓인 이 PR의 최종 상태는 demo/portal-v1 브랜치와 demo-portal-v1.0.0 태그에 보존했습니다. 따라서 feature base 병합 없이 이 PR을 닫습니다.