fix(daemons): block owner transfer while assigned

docs/interface-contract.md

@@ -126,6 +126,7 @@
 - Each asset (portfolio) may be assigned to exactly one daemon via `portfolios.managed_by_daemon_id`. Mismatch or unassigned asset → HTTP 403 on ledger writes.
 - **Token rebind** (BAT-007/REQ-023): `pfhub service-token rebind <name> --daemon-id <id>` — daemon_id 변경, runtime_id 불변. 대상 daemon은 active이어야 하고 token 소유 user와 일치해야 한다.
 - **Daemon deactivation** (BAT-007/REQ-022): `pfhub daemon update <daemon_id> --deactivate --force` — daemon is_active=false + 바인딩된 모든 service token 즉시 revoke.
+- **Admin daemon owner transfer**: `PATCH /v1/admin/daemons/{daemon_id}` with a changed `owner_user_id` is allowed only for an unassigned daemon. A referenced daemon returns HTTP 409; no daemon owner, portfolio assignment, or broker credential is changed. Owner transfer locks the daemon row `FOR UPDATE`, while portfolio assignment locks it `FOR SHARE`, so a concurrent operation either transfers first and rejects the old owner's assignment as HTTP 404 or assigns first and rejects the transfer as HTTP 409.
 - **NULL daemon migration CLI** (BAT-007/REQ-023): `pfhub service-token migrate-null-daemon --dry-run` — NULL daemon_id active service token inventory 출력 + user별 candidate daemon 목록. `--dry-run` 없이 실행 시 exit code 1 + 수동 안내.
 
 ### Endpoint: `GET /v1/assets`
@@ -570,4 +571,4 @@
 - 2026-05-13 KST: bat-010 — REQ-006/007/008/011/023: added daemon authorization model section; updated GET /v1/assets (daemon-scoped filter, NULL 403); updated GET /v1/user_info (daemon_id field, NULL runtime_id → 200+null diagnostic); updated POST /v1/assets/{asset_id}/ledger/trades (daemon assignment authorization, fail-closed policy); added daemon CLI subcommand to CLI surface; updated v1 purpose and source discovery.
 - 2026-05-11 KST: bat-008 — REQ-011 AC-1: expanded v1 Consumer API section with authentication contract, detailed request/response schemas for GET /v1/assets, GET /v1/user_info, POST /v1/assets/{asset_id}/ledger/trades; updated GET /health response schema (REQ-004); added idempotency contract.
 - 2026-05-11 KST: bat-006 — Added v1 consumer API interface section (trex-basic); noted asset_id UUID change and simultaneous deployment constraint; updated CLI portfolio inputs to reflect name+user identification.
-- 2026-04-30 KST: Bootstrap baseline created from repository observation for initial StagePilot adoption.
+- 2026-04-30 KST: Bootstrap baseline created from repository observation for initial StagePilot adoption.