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/web/src/lib/i18n/en.ts

@@ -419,6 +419,8 @@ export const en: Catalog = {
     scan: "Scan for controllers",
     scanning: "Scanning…",
     noControllersFound: "No controllers found on the LAN.",
+    usbNoneFound: "No USB printer found (/dev/usb/lpN) — check cable/power; the path can be typed manually.",
+    usbSavedMissing: "saved — not present now",
     use: "Use",
     test: "Test connection",
     testing: "Testing…",