Rongta 80mm printer: driver, role-based failover, live status monitoring

Add the rongta PrinterDevice driver (ESC/POS over raw TCP 9100) and the
device-agnostic pieces around it:

- Roles + failover: each printer declares a role (entry-dispenser/booth-
  receipt) and failoverRank; printer-routing.ts picks the best healthy printer
  and falls back outside->booth for entry tickets (never the reverse).
- Live status: MonitorableDevice.readStatus()/PrinterStatus capability. The
  Rongta driver scrapes the device's own /prn_stat.htm (Cover/Cutter/Paper
  End/Near End/Off-Line) rather than hand-decoding DLE EOT, whose reply bytes
  on this clone don't match the canonical ESC/POS bit layout (verified on
  hardware) -- avoids a false-healthy. Maps to ready/degraded/offline, fail
  safe on an unreachable or unexpected page.
- Server PrinterMonitor polls enabled printers (PRINTER_POLL_MS, default 5s),
  caches latest, emits "printer-status" on change. Exposed via
  GET /api/printers/status and an SSE stream for the booth UI.

Verified against 10.0.10.6: ready when healthy, offline when unreachable
(no throw), bus emits on change and suppresses unchanged reads.

Wiki: new rongta-printer entity, printer-roles-failover and
printer-status-monitoring concepts; BOM/index/log updated.

apps/server/src/device-events.ts

@@ -1,4 +1,5 @@
 import { EventEmitter } from "node:events";
+import type { PrinterStatus } from "@parking/devices";
 
 // Internal event bus for device-originated events (button presses, etc.).
 // Hardware drivers / inbound device pushes emit here; business logic (entry
@@ -14,6 +15,15 @@ export interface DeviceInputEvent {
   readonly source: "push" | "poll";
 }
 
+/** A printer's status as tracked by the live monitor (status + identity). */
+export interface PrinterStatusEvent {
+  readonly deviceId: string; // lane_devices id
+  readonly lane: number;
+  readonly driverId: string;
+  readonly role?: string; // entry-dispenser | booth-receipt
+  readonly status: PrinterStatus;
+}
+
 class DeviceEventBus extends EventEmitter {
   emitInput(event: DeviceInputEvent): void {
     this.emit("input", event);
@@ -22,6 +32,15 @@ class DeviceEventBus extends EventEmitter {
     this.on("input", cb);
     return () => this.off("input", cb);
   }
+
+  /** Emitted by the printer monitor whenever a printer's status CHANGES. */
+  emitPrinterStatus(event: PrinterStatusEvent): void {
+    this.emit("printer-status", event);
+  }
+  onPrinterStatus(cb: (event: PrinterStatusEvent) => void): () => void {
+    this.on("printer-status", cb);
+    return () => this.off("printer-status", cb);
+  }
 }
 
 /** Process-wide device event bus. */