docs: finish questions consolidation — drop merged files [#344]

Leftover unstaged state from the parallel 09-02 sessions: delete
questions-v1/v2, HomeAssistant/needfromcharles.md, night-grind-plan.md
(content lives in questions-09022206.md / questions-v3.md / git history);
drop superseded UniFi API-key ask (#619 multicast fix made it moot).

Details: https://projects.knownelement.com/issues/344#note-3911

questions-09022206.md

@@ -2,8 +2,8 @@
 # questions-09022206.md — consolidated open asks (2026-09-02)
 
 > Merged from `questions-v2.md` (repo root) + `HomeAssistant/needfromcharles.md`
-> per founder request. That file is now a pointer; questions-v2.md stays as
-> history. Answer inline; agent checks before asking again.
+> per founder request; both source files since removed (history in git).
+> Answer inline; agent checks before asking again.
 
 ## HA / monitoring (was needfromcharles)
 
@@ -25,9 +25,6 @@ Integration live (key+account+MQTT); account has ZERO cloud devices = BLE-only.
 ### 4. Emporia Vue 3 — blocks #623 (BTU loop)
 - [ ] Ordered? ETA:
 
-### 8. UniFi Integration API key — LOW priority now (multicast fix works)
-- [ ] (optional) Settings → System → Advanced → Integrations → API Keys
-
 ### 9. iDRAC — RESOLVED 2026-09-02
 [x] Creds worked; both SNMP agents live; tsys6 `public` accepted by founder.