Two findings from review:
1. callAI() previously accepted any model string from the client.
POST /api/hpi with { model: "openai/o1" } would call the reasoning
model regardless of whether the operator enabled it. Added
getAllowedModelIds() in src/utils/models.js (60s TTL DB-backed
cache) and a guard at the top of callAI() that rejects with
"model_not_permitted" when the requested ID isn't in the active
roster. No model supplied → silent fallback to DEFAULT_MODEL.
2. Middleware was updating user_sessions.last_activity on every
request, including GETs. Client-side polling (/api/auth/me
heartbeats, dashboard refreshes, log tail calls) kept sessions
alive indefinitely, defeating the 24h sliding idle policy. Now
only POST/PUT/DELETE/PATCH count as "user activity". GETs are
read-only and often automated — they no longer extend the
session. Idle enforcement still runs on every method, so a
24h-idle user still gets kicked on their next GET.
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