feat(setup): USB printer discovery — pick a real /dev/usb device

The kernel numbers usblp nodes by plug/boot order (park-buzi's printer
is lp1); the wizard hardcoded lp0 in labels/default and the admin had to
shell in and `ls /dev/usb`. Now:

- GET /api/setup/usb-printers enumerates /dev/usb/lpN (visible via the
  compose bind-mount) and enriches each with the printer's self-reported
  make/model from sysfs ieee1284_id (readable through Docker's ro /sys).
- The wizard's devicePath becomes a SELECT of printers actually present
  ("/dev/usb/lp1 — Xprinter XP-K200L"): a fresh form preselects the
  first real device; a saved-but-unplugged path stays selectable,
  flagged "saved — not present now"; zero found falls back to free text
  + a check-the-cable hint.
- Transport option label no longer hardcodes lp0.

Wiki: printer-usb-transport marked HARDWARE-VERIFIED (lab 2026-07-07:
full slip + feed + cut over USB — parity with TCP).

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

apps/server/src/routes/setup.ts

@@ -560,6 +560,39 @@ export async function setupRoutes(
     },
   );
 
+  // USB printers PRESENT on the box: enumerate /dev/usb/lpN (the usblp nodes the
+  // container sees via the /dev/usb bind-mount) and enrich each with the printer's
+  // self-reported make/model from sysfs (ieee1284_id — readable through Docker's
+  // default ro /sys). The wizard offers these as a SELECT so the admin never has to
+  // shell in and `ls /dev/usb` to learn the kernel picked lp1 (field friction,
+  // park-buzi 2026-07-07). Empty list = no usblp printer plugged/visible.
+  app.get("/api/setup/usb-printers", { preHandler: adminGuard }, async () => {
+    const { readdir, readFile } = await import("node:fs/promises");
+    let names: string[] = [];
+    try {
+      names = (await readdir("/dev/usb")).filter((n) => /^lp\d+$/.test(n)).sort();
+    } catch {
+      return { printers: [] }; // no /dev/usb at all — nothing plugged (or no mount)
+    }
+    const printers = await Promise.all(
+      names.map(async (n) => {
+        // ieee1284_id: "MFG:Xprinter;CMD:ESCPOS;MDL:XP-K200L;…" — best-effort.
+        let description: string | null = null;
+        try {
+          const id = await readFile(`/sys/class/usbmisc/${n}/device/ieee1284_id`, "utf8");
+          const pick = (key: string) => id.match(new RegExp(`(?:^|;)\\s*${key}:([^;]+)`, "i"))?.[1]?.trim();
+          const mfg = pick("MFG") ?? pick("MANUFACTURER");
+          const mdl = pick("MDL") ?? pick("MODEL");
+          description = [mfg, mdl].filter(Boolean).join(" ") || null;
+        } catch {
+          /* sysfs not readable / attribute absent — path alone is still useful */
+        }
+        return { path: `/dev/usb/${n}`, description };
+      }),
+    );
+    return { printers };
+  });
+
   // Assign a device. Validates the chosen driver + config, configures the device
   // (fix preconditions + set up Digest-authenticated input push — no manual device-
   // web-UI step by the admin), then persists. Fails the save if the device can't be