feat(19-ui-integration): przycisk Drukuj, bulk print, kolejka wydruku

- Przycisk "Drukuj" w prepare.php i show.php z AJAX + duplikat protection
- Bulk print z listy zamówień (checkboxy + header action)
- Kolejka wydruku w Ustawienia > Drukowanie (filtr statusu, retry)
- POST /api/print/jobs/bulk endpoint (package_ids + order_ids)
- ensureLabel() auto-download przez ShipmentProviderRegistry
- Apaczka carrier_id = nazwa usługi, kolumna Przewoznik
- Tab persistence (localStorage), label file_exists check
- Fix use statement ApaczkaApiClient, redirect po utworzeniu przesyłki
- Phase 17 (receipt duplicate guard) + Phase 18 (print queue backend) docs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/assets/css/app.css

@@ -441,6 +441,60 @@
   margin: 0;
 }
 
+.print-status-badge {
+  display: inline-block;
+  padding: 2px 8px;
+  border-radius: 3px;
+  font-size: 0.75rem;
+  font-weight: 600;
+  line-height: 1.4;
+}
+.print-status-badge--pending {
+  background-color: #fff3cd;
+  color: #856404;
+}
+.print-status-badge--completed {
+  background-color: #d4edda;
+  color: #155724;
+}
+.print-status-badge--failed {
+  background-color: #f8d7da;
+  color: #721c24;
+}
+
+.print-queue-filters {
+  display: flex;
+  gap: 4px;
+}
+
+.print-queue-table td, .print-queue-table th {
+  padding: 6px 8px;
+  font-size: 0.85rem;
+}
+
+.btn--outline-primary {
+  background: transparent;
+  border: 1px solid #4a90d9;
+  color: #4a90d9;
+  cursor: pointer;
+  border-radius: 3px;
+  font-size: 0.75rem;
+  padding: 3px 8px;
+  transition: background-color 0.15s, color 0.15s;
+}
+.btn--outline-primary:hover {
+  background-color: #4a90d9;
+  color: #fff;
+}
+.btn--outline-primary:disabled {
+  opacity: 0.6;
+  cursor: not-allowed;
+}
+.btn--outline-primary.is-success {
+  border-color: #28a745;
+  color: #28a745;
+}
+
 * {
   box-sizing: border-box;
 }