[feat:] im- and export (pdf/json)

Program.cs

@@ -1,5 +1,7 @@
 using Avalonia;
 using System;
+using PdfSharp;
+using PdfSharp.Fonts;
 
 namespace spplus;
 
@@ -9,8 +11,14 @@ class Program
     // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
     // yet and stuff might break.
     [STAThread]
-    public static void Main(string[] args) => BuildAvaloniaApp()
-        .StartWithClassicDesktopLifetime(args);
+    public static void Main(string[] args)
+    {
+        // Initialize PdfSharp font resolver before any PDF operations
+        GlobalFontSettings.FontResolver = new CustomFontResolver();
+        
+        BuildAvaloniaApp()
+            .StartWithClassicDesktopLifetime(args);
+    }
 
     // Avalonia configuration, don't remove; also used by visual designer.
     public static AppBuilder BuildAvaloniaApp()