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/UiKit.cs

@@ -8,7 +8,7 @@ using System.Windows.Media;
 using System.Windows.Media.Animation;
 using System.Windows.Media.Effects;
 
-namespace KillerPDF
+namespace MmdPdf
 {
     // WPF has no built-in animation for GridLength, so grid columns (the sidebar) can only snap.
     // This drives a pixel-unit GridLength between From and To so a column glides instead.
@@ -466,7 +466,7 @@ namespace KillerPDF
         // Dialog/popup buttons. accent==true is the primary (fills solid accent on hover); false is secondary.
         public static Button Make(object content, bool accent)
         {
-            if (KillerPDF.Services.ThemeManager.Current == KillerPDF.Services.Theme.SE98)
+            if (MmdPdf.Services.ThemeManager.Current == MmdPdf.Services.Theme.SE98)
             {
                 var button = Make(content, Brush("ChipFaceBrush"), Brush("ChipFaceBrush"),
                                   Brush("TextBrush"), Brush("TextBrush"), Brushes.Transparent);