wiki: record JWT key open question; defer ESP32 controller

- open-questions #7: symmetric vs. asymmetric JWT signing key (from the
  commit security review). Prefer RS256/EdDSA so verifying hosts hold only a
  public key — mirrors the ATECC608 / challenge-response "public key only"
  property. Decide before multi-host/multi-lane deployment.
- Mark esp32-custom-controller status: deferred per decision not to build
  device-level auth now; access control stays on UHPPOTE + network isolation
  (noted in open-questions #6).
- local-jwt-auth: document hardened secret handling + 8h expiry and the
  asymmetric-key pointer.
- Update index.md and append a log.md entry.

wiki/entities/local-jwt-auth.md

@@ -2,7 +2,7 @@
 type: entity
 tags: [parking, stack, auth, offline-first]
 sources: [parking-system-architecture]
-updated: 2026-06-14
+updated: 2026-06-15
 ---
 
 # Local JWT Auth
@@ -11,9 +11,15 @@ Authentication and authorization, kept **fully local** — a direct consequence
 [[offline-first]] (an air-gapped park cannot reach an external identity provider; see
 [[logto-zitadel-oidc]] for the rejected alternative). (See [[parking-system-architecture]] §2.)
 
-- `@fastify/jwt` signs tokens with a **local secret**.
+- `@fastify/jwt` signs tokens with a **local secret** (symmetric HMAC). The server **refuses to
+  start** without a strong `JWT_SECRET` (≥32 chars, no placeholder) — there is deliberately no
+  insecure default — and mints tokens with an **8h expiry** (bound to a shift).
 - A `users` table in [[sqlite]] holds **bcrypt** password hashes plus a **role** column.
 - Authorization = a simple `preHandler` role guard per route: **admin / operator / cashier /
   readonly**. No Casbin or full RBAC engine needed at this scale.
 
+> **Open decision:** moving from the symmetric secret to an **asymmetric key (RS256/EdDSA)** so
+> verifying hosts hold only a public key — [[open-questions]] #7. Relevant before any
+> multi-host/multi-lane deployment.
+
 Part of the [[technology-stack]]. License: MIT.