feat: show recognized plate in live feed + active sessions

Surface the advisory ANPR plate (device_events kind="read", keyed by
session identity — unsigned, prunable, never an access decision) next to
entry/exit events in the live feed and on active-session rows.

Resolved at serialize time (new plate-lookup.ts; prefers an entry read;
one device_events scan per page) like subscriber-name enrichment — the
signed ledger is untouched. Adds plate? to the shared LedgerEvent and to
ActiveSession/SessionLookup; a small amber badge in the UI.

Caveat: a vehicle_entry is signed + pushed over WS before the async ANPR
read lands, so a fresh feed row may show no plate until reload; always
present on active sessions.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/BoothScreen.tsx

@@ -165,7 +165,17 @@ function EventRow({ e, onOpen }: { e: LedgerEvent; onOpen: (e: LedgerEvent) => v
     >
       <span className="text-term-muted">{hhmmss(e.occurredAt)}</span>
       <span className={`shrink-0 font-semibold ${style?.color ?? "text-term-text"}`}>{label}</span>
-      <span className="truncate text-term-text">{displayIdentity(e)}</span>
+      <span className="flex min-w-0 items-center gap-2">
+        <span className="truncate text-term-text">{displayIdentity(e)}</span>
+        {e.plate && (
+          <span
+            className="shrink-0 rounded border border-term-border px-1 text-[11px] font-semibold tracking-wide text-term-amber"
+            title={t("booth.plateTitle")}
+          >
+            {e.plate}
+          </span>
+        )}
+      </span>
       <span className="text-term-muted">#{e.index}</span>
       {showDetail && (
         <div className="col-start-3 col-end-5 flex flex-wrap items-center gap-x-2 gap-y-1">