[MQ7] Terminate quest flow (confirm, set status, disable new links/answers)

[zhn1010]

Priority: High
Type: Implementation
Est: 3h
Original Ref: MQ7

Dependencies

• [QS-IMP1] Implement status/health compute function and expose via APIs (home/link/manage) #63
• [AUTH1] Enforce auth/role on new mutations (link create, proposed answer, leads decisions, termination, chat send, gift card) #110
• [N-EMIT2] Implement emitters; wire into mutations (QL1, QL2, MQ2, MQ7, LP1, QL5) to write/publish notifications #98