feat(booth): live lane busy/free barrier lights from camera vehicle detection

A Hikvision vehicle detection (eventType=VMD, targetType=vehicle) on a
camera bound to entry/exit now marks that lane "busy" and shows it as a
barrier light beside the scan input on the booth (green=free, red=busy).
Advisory only — it gates nothing (never blocks a ticket or opens a barrier).

- Parse eventState (active/inactive) from the Hik payload.
- LaneStatus tracker: a vehicle `active` event marks the camera's bound lane
  busy + arms an auto-clear timer. This camera class sends no leave/`inactive`
  signal, so "free" is timeout-driven (LANE_BUSY_TTL_MS, default 90s; the
  camera re-fires `active` while a car sits there, refreshing the timer). A
  "both"-direction camera marks both lanes.
- Push lane-status over the existing booth WS (+ in the hello snapshot);
  live-store holds { entry, exit }; two BarrierLight icons render it.
- i18n booth.laneEntry/laneExit (sq + en).

Tests: lane-status.test.ts (7 — busy/free, TTL auto-clear, timer re-arm,
no re-emit while busy, both/exit direction, unknown device). server 120/120;
web + server build/lint green.

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

apps/server/src/device-events.ts

@@ -76,6 +76,16 @@ export interface DeviceStatusEvent {
   readonly checkedAt: string; // ISO-8601
 }
 
+/** Lane occupancy from a camera's vehicle detection — a per-direction "busy/free"
+ *  the booth shows as barrier lights. ADVISORY ONLY: a detection is a hint, never a
+ *  gate (it never blocks a ticket or opens a barrier). "busy" is set by a vehicle
+ *  `active` event; it auto-clears to "free" after a timeout (this camera class sends
+ *  no leave/`inactive` signal — see wiki/entities/lpr-camera.md). */
+export interface LaneStatusEvent {
+  readonly entry: boolean; // true = busy (a vehicle is at the entry vicinity)
+  readonly exit: boolean; // true = busy (a vehicle is at the exit vicinity)
+}
+
 class DeviceEventBus extends EventEmitter {
   emitInput(event: DeviceInputEvent): void {
     this.emit("input", event);
@@ -128,6 +138,16 @@ class DeviceEventBus extends EventEmitter {
     this.on("ledger", cb);
     return () => this.off("ledger", cb);
   }
+
+  /** Emitted whenever a lane's busy/free state CHANGES (from camera vehicle
+   *  detection). Drives the booth's barrier lights. Advisory only. */
+  emitLaneStatus(event: LaneStatusEvent): void {
+    this.emit("lane-status", event);
+  }
+  onLaneStatus(cb: (event: LaneStatusEvent) => void): () => void {
+    this.on("lane-status", cb);
+    return () => this.off("lane-status", cb);
+  }
 }
 
 /** Process-wide device event bus. */