[N-EMIT2] Implement emitters; wire into mutations (QL1, QL2, MQ2, MQ7, LP1, QL5) to write/publish notifications

[zhn1010]

Priority: High
Type: Implementation
Est: 4h
Original Ref: N-EMIT2

Dependencies

• [N-EMIT1] Define notification emitters for events (reflow, node join, proposed answer lifecycle, termination, chat message) #97
• [AUTH1] Enforce auth/role on new mutations (link create, proposed answer, leads decisions, termination, chat send, gift card) #110