docs: add rel-003, rel-004 releases and update CLI user scoping implementation

Release: REL-003_20260512 — CLI user scoping and local DB ops runbook

Requirements & Batches:
- BAT-003 (REQ-013): portfolio list --user required enforcement with owner filtering
- BAT-004 (REQ-014): portfolio create --user required enforcement with owner assignment
- BAT-007 (REQ-001/002/003): local DB validation runbook and baseline docs update

CLI Enhancements:
- Update user.py: add username-based user lookup (get_by_username)
- Add UserDetailResponse schema with service token listing
- Update list_service_tokens API in user_service.py
- Enhance user detail display with service token information
- Add service_token_count and service_token_names to user responses

Testing:
- Add comprehensive test coverage in test_cli.py for user commands
- Validate username-based lookup functionality

Release: REL-004_20260512 — Portfolio UUID migration and API UUID switch

Requirements & Batches:
- BAT-006 (REQ-016/017/018): portfolio UUID migration complete
- BAT-008 (REQ-019): baseline documentation update for UUID migration

Breaking Changes (REL-003):
- portfolio list requires --user <username> parameter
- portfolio create requires --user <username> parameter

Documentation:
- Create rel-003 and rel-004 release documents with rollout and rollback plans
- Update docs/releases/index.md with new releases
- Update README.md with CLI user scoping clarification
- Sync all release verification checklists and deployment notes

README.md

@@ -102,7 +102,7 @@ The same commands are also available through the shorter alias `phub`.
 pfhub --help
 pfhub user list
 pfhub user create --username alice --password password123 --email alice@example.com --force
-pfhub user get <user-id>
+pfhub user get <username>
 pfhub user update <user-id> --username alice-updated --force
 pfhub user delete <user-id> --force
 pfhub service-token issue nightly --user alice --ttl-days 30