feat(setup): print a real test slip from the printer "Test connection" modal

healthCheck only opens the transport (TCP connect / USB open) — it proves the
printer is REACHABLE, not that paper feeds and the head fires. Add a "Print test
slip" action so the admin can physically confirm a printer is live (the new
host-net USB /dev/usb/lpN path, or a network printer).

- server: POST /api/setup/test-print — printer-only, re-merges stored secrets like
  /test (so an edited network printer authenticates), creates the device, and pushes
  a short slip via the device-agnostic printReport(). Fail-soft: a print error
  (paper out, head fault, transport drop) is reported, never a 500. Mirrors the
  test-anpr pattern.
- web: testPrint() client + PrintTestResult; a button in the device modal shown for
  category=printer, with ok/fail rendering. i18n keys in sq + en (parity holds).

Server 168 tests pass; web + server typecheck clean.

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

apps/web/src/lib/i18n/sq.ts

@@ -416,6 +416,13 @@ export const sq = {
     "anprFail.vision-disabled": "Shërbimi i vizionit është çaktivizuar — aktivizoje (VISION_ENABLED) për ta testuar ANPR.",
     "anprFail.snapshot-failed": "Nuk u mor dot pamje nga kamera (jashtë linje ose e paarritshme).",
     "anprFail.no-plate": "Nuk u gjet asnjë targë në pamje.",
+    // Printer test slip — pushes a real slip so the admin can confirm it physically prints.
+    testPrint: "Printo provë",
+    printTesting: "Duke printuar…",
+    testPrintHint:
+      "Dërgon një fletë prove te printeri tani. ‘I lidhur’ vetëm hap lidhjen — kjo konfirmon se printeri vërtet nxjerr letër.",
+    printOk: "✓ Fleta e provës u dërgua ({{ms}} ms). Kontrollo printerin.",
+    "printFail.print-failed": "Printeri nuk pranoi punën (pa letër, kapaku hapur, ose lidhja ra).",
     // Alarm Server push settings — generated for the camera's Event → Alarm Server form.
     alarmUrlTitle: "Cilësimet e Alarm Server (vendosi te kamera)",
     alarmUrlHint: