feat: rebrand to MMD PDF, single corporate theme, and remove original text under an edit

- Services/PdfRedactText.cs: strip text whose origin falls inside a CoverAnnotation
  from the page content stream at save time, hooked into PdfBurn.DrawAnnotationsIntoDoc.
  Fixes edited values staying recoverable by text extraction.
- Themes/MMD.xaml replaces all thirteen themes; picker and accent strip removed; no dark mode.
- Rename KillerPDF -> MMD PDF across code, resources, packaging and locale strings; new icon.
- Remove the upstream author credit and the in-app install button.

Controls/PrintPreviewWindow.cs

@@ -13,10 +13,10 @@ using System.Windows.Media.Imaging;
 using Docnet.Core;
 using Docnet.Core.Models;
 
-namespace KillerPDF
+namespace MmdPdf
 {
     /// <summary>
-    /// KillerPDF's own print dialog with a working preview. WPF's built-in PrintDialog
+    /// MmdPdf's own print dialog with a working preview. WPF's built-in PrintDialog
     /// reports "This app doesn't support print preview", so we render the rasterized
     /// pages ourselves, expose printer / orientation / copies / page-range settings,
     /// and drive the spooler via a non-UI PrintDialog when the user clicks Print.
@@ -581,7 +581,7 @@ namespace KillerPDF
             };
             panel.Children.Add(margins);
 
-            // Pages per sheet (N-up): KillerPDF composes the sheet itself.
+            // Pages per sheet (N-up): MmdPdf composes the sheet itself.
             panel.Children.Add(Label(S("Str_Print_PagesPerSheet")));
             var nup = new ComboBox { Margin = new Thickness(0, 4, 0, 12), Height = 26 };
             ApplyComboStyle(nup);
@@ -1208,7 +1208,7 @@ namespace KillerPDF
         {
             if (_queue == null)
             {
-                KillerDialog.Show(this, S("Str_Dlg_NoPrinter"), "KillerPDF",
+                KillerDialog.Show(this, S("Str_Dlg_NoPrinter"), "MmdPdf",
                     MessageBoxButton.OK, MessageBoxImage.Warning);
                 return;
             }
@@ -1218,7 +1218,7 @@ namespace KillerPDF
             var indices = SelectedIndices();
             if (indices.Count == 0)
             {
-                KillerDialog.Show(this, S("Str_Dlg_NoValidPages"), "KillerPDF",
+                KillerDialog.Show(this, S("Str_Dlg_NoValidPages"), "MmdPdf",
                     MessageBoxButton.OK, MessageBoxImage.Warning);
                 return;
             }
@@ -1285,7 +1285,7 @@ namespace KillerPDF
                         if (idx < 0 || idx >= _pages.Length) continue;
                         using var pr = dr.GetPageReader(idx);
                         int w = pr.GetPageWidth(), h = pr.GetPageHeight();
-                        var pixels = KillerPDF.Services.PdfiumInterop.RenderPageWithAnnotations(_renderPath, idx, w, h)
+                        var pixels = MmdPdf.Services.PdfiumInterop.RenderPageWithAnnotations(_renderPath, idx, w, h)
                             ?? pr.GetImage();
                         var bs = BitmapSource.Create(w, h, 96, 96, PixelFormats.Bgra32, null, pixels, w * 4);   // #141
                         bs.Freeze();
@@ -1318,7 +1318,7 @@ namespace KillerPDF
                 // been retyped behind the scrim, and a range that now matches nothing must stay disabled.
                 UpdatePreview();
                 KillerDialog.Show(this, S("Str_Err_PrintFailed") + "\n" + ex.GetType().Name + ": " + ex.Message,
-                    "KillerPDF", MessageBoxButton.OK, MessageBoxImage.Error);
+                    "MmdPdf", MessageBoxButton.OK, MessageBoxImage.Error);
             }
         }
 
@@ -1366,7 +1366,7 @@ namespace KillerPDF
             // STA: both the XPS serializer and the spooler reach apartment-bound COM underneath.
             thread.SetApartmentState(System.Threading.ApartmentState.STA);
             thread.IsBackground = true;
-            thread.Name = "KillerPDF print spool";
+            thread.Name = "MmdPdf print spool";
             thread.Start();
             return done.Task;
         }