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/server.ts

@@ -3,8 +3,10 @@ import jwt from "@fastify/jwt";
 import Fastify, { type FastifyInstance } from "fastify";
 import { createDb, type Db } from "@parking/db";
 import { TOKEN_COOKIE, requireJwtSecret } from "./auth.js";
+import { PrinterMonitor } from "./printer-monitor.js";
 import { authRoutes } from "./routes/auth.js";
 import { deviceRoutes } from "./routes/devices.js";
+import { printerRoutes } from "./routes/printers.js";
 import { setupRoutes } from "./routes/setup.js";
 
 // The backend is Fastify (Node). Hardware drivers live as isolated Fastify
@@ -49,6 +51,14 @@ export async function buildServer(opts: BuildOptions = {}): Promise<FastifyInsta
   // the device's lane_devices config (written on assign).
   await deviceRoutes(app, db);
 
+  // Live printer-status monitor: polls printers (paper/cover/cutter/offline) and
+  // pushes changes to the booth UI. setupRoutes() has already registered the
+  // built-in drivers the monitor needs. See wiki/concepts/printer-status-monitoring.md.
+  const printerMonitor = new PrinterMonitor(db, app.log);
+  await printerRoutes(app, printerMonitor);
+  app.addHook("onReady", async () => printerMonitor.start());
+  app.addHook("onClose", async () => printerMonitor.stop());
+
   // TODO: entry flow (input event → signed event → print → relay), event-log routes.
 
   return app;