feat(20-windows-client): aplikacja C# WinForms do zdalnego druku etykiet

- System tray app z NotifyIcon + ContextMenuStrip
- Polling API orderPRO (GET /api/print/jobs/pending)
- Pobieranie etykiet PDF i druk przez PdfiumViewer
- Formularz ustawień: URL API, klucz, drukarka, interwał
- Okno logów z historią (ciemny motyw, Consolas)
- Self-contained .NET 8 publish (win-x64)
- Milestone v0.7 Zdalne drukowanie etykiet — COMPLETE

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

clients/windows/OrderPROPrint/Models/PrintJob.cs

@@ -0,0 +1,24 @@
+using System.Text.Json.Serialization;
+
+namespace OrderPROPrint.Models;
+
+public class PendingJobsResponse
+{
+    [JsonPropertyName("jobs")]
+    public List<PrintJob> Jobs { get; set; } = new();
+}
+
+public class PrintJob
+{
+    [JsonPropertyName("id")]
+    public int Id { get; set; }
+
+    [JsonPropertyName("order_number")]
+    public string OrderNumber { get; set; } = "";
+
+    [JsonPropertyName("tracking_number")]
+    public string TrackingNumber { get; set; } = "";
+
+    [JsonPropertyName("created_at")]
+    public string CreatedAt { get; set; } = "";
+}