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/SetupWizard.tsx

@@ -9,8 +9,10 @@ import {
   fetchState,
   testAnpr,
   testDevice,
+  testPrint,
   unassignDevice,
   type AnprTestResult,
+  type PrintTestResult,
   type Assignment,
   type BackendIpCandidate,
   type ButtonLightSpec,
@@ -339,6 +341,7 @@ function DeviceForm({
   const pushesToBackend = selected != null && pushCapableIds.includes(selected.id);
   const isController = category === "access";
   const isCamera = category === "camera";
+  const isPrinter = category === "printer";
   // ANPR opt-in for a camera: when true, the VisionReader polls this camera for plates
   // (config.anpr). Off by default. See wiki/entities/opencv-anpr-service.md.
   const [anpr, setAnpr] = useState<boolean>(editCfg?.anpr === true);
@@ -380,6 +383,10 @@ function DeviceForm({
   const [anprResult, setAnprResult] = useState<AnprTestResult | null>(null);
   const [anprTesting, setAnprTesting] = useState(false);
   const [anprError, setAnprError] = useState<string | null>(null);
+
+  const [printResult, setPrintResult] = useState<PrintTestResult | null>(null);
+  const [printTesting, setPrintTesting] = useState(false);
+  const [printError, setPrintError] = useState<string | null>(null);
   const [saving, setSaving] = useState(false);
   const [saveError, setSaveError] = useState<string | null>(null);
   const [found, setFound] = useState<DiscoveredDevice[] | null>(null);
@@ -531,6 +538,23 @@ function DeviceForm({
     }
   }
 
+  // Push a real test slip to the printer — proves it physically prints (healthCheck
+  // only opens the transport). Passes editing?.id so an edited network printer's
+  // stored secrets re-merge. Never blocks save.
+  async function testPrintNow() {
+    if (!selected) return;
+    setPrintTesting(true);
+    setPrintError(null);
+    setPrintResult(null);
+    try {
+      setPrintResult(await testPrint(selected.id, mergedScalarConfig(), editing?.id));
+    } catch (e) {
+      setPrintError((e as Error).message);
+    } finally {
+      setPrintTesting(false);
+    }
+  }
+
   async function save() {
     if (!selected) return;
     // Bound devices must point at a controller relay (binding is optional in the
@@ -867,6 +891,30 @@ function DeviceForm({
             </div>
           )}
 
+          {/* PRINTER: push a real test slip so the admin can confirm it physically
+              prints (healthCheck only opens the transport / USB node). */}
+          {isPrinter && (
+            <div className="mt-3 rounded-term border border-term-border bg-term-bg p-2">
+              <button type="button" className="btn btn-sm" onClick={testPrintNow} disabled={printTesting}>
+                {printTesting ? t("setup.printTesting") : t("setup.testPrint")}
+              </button>
+              <p className="hint mt-1">{t("setup.testPrintHint")}</p>
+
+              {printError && <p className="mt-2 text-[12px] text-term-red">{t("setup.testFailed", { error: printError })}</p>}
+              {printResult &&
+                (printResult.ok ? (
+                  <div className="mt-2 text-[12px] text-term-green">
+                    {t("setup.printOk", { ms: printResult.tookMs })}
+                  </div>
+                ) : (
+                  <div className="mt-2 text-[12px] text-term-amber">
+                    ⚠ {t(`setup.printFail.${printResult.reason}`, { defaultValue: printResult.reason })}
+                    {printResult.detail && <span className="text-term-muted"> — {printResult.detail}</span>}
+                  </div>
+                ))}
+            </div>
+          )}
+
           {backendIps && backendIps.length > 0 && (
             <div className="mt-3">
               <div className="field max-w-md">