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/SignDocumentDialog.cs

@@ -7,16 +7,16 @@ using System.Windows.Controls;
 using System.Windows.Data;
 using System.Windows.Input;
 using System.Windows.Media;
-using KillerPDF.Services.Signing;
+using MmdPdf.Services.Signing;
 using Microsoft.Win32;
 
-namespace KillerPDF
+namespace MmdPdf
 {
     /// <summary>
     /// Themed modal dialog that cryptographically signs the open PDF with a certificate (a .pfx/.p12
     /// file, or one from the Windows store) and writes a NEW signed copy. This is the real digital
     /// signature - distinct from the drawn "Signature" stamp tool, which only places a picture.
-    /// Chrome and colors mirror PrintPreviewWindow so every KillerPDF dialog looks identical.
+    /// Chrome and colors mirror PrintPreviewWindow so every MmdPdf dialog looks identical.
     /// </summary>
     internal sealed class SignDocumentDialog : Window
     {
@@ -45,7 +45,7 @@ namespace KillerPDF
         public SignDocumentDialog(Window? owner, string sourcePdf)
         {
             _sourcePdf = sourcePdf;
-            Title = "KillerPDF - " + L("Str_Sign_Name");
+            Title = "MmdPdf - " + L("Str_Sign_Name");
             Width = 470;
             SizeToContent = SizeToContent.Height;
             UseLayoutRounding = true;
@@ -149,7 +149,7 @@ namespace KillerPDF
 
             SyncSource();
 
-            Content = DialogChrome.Frame(this, Owner, "KillerPDF - " + L("Str_Sign_TitleSuffix"),
+            Content = DialogChrome.Frame(this, Owner, "MmdPdf - " + L("Str_Sign_TitleSuffix"),
                 () => { DialogResult = false; Close(); }, body);
         }
 
@@ -170,14 +170,14 @@ namespace KillerPDF
 
         private void BrowsePfx()
         {
-            var dlg = new KillerPDF.Controls.FileDialog(KillerPDF.Controls.FileDialogMode.Open)
+            var dlg = new MmdPdf.Controls.FileDialog(MmdPdf.Controls.FileDialogMode.Open)
                           { Filter = L("Str_Filter_Cert") + "|*.pfx;*.p12|" + L("Str_Filter_AllFiles") + "|*.*", Title = L("Str_Sign_ChooseCert") };
             if (dlg.ShowDialog(this) == true) _pfxBox.Text = dlg.FileName;
         }
 
         private void BrowseOutput()
         {
-            var dlg = new KillerPDF.Controls.FileDialog(KillerPDF.Controls.FileDialogMode.Save)
+            var dlg = new MmdPdf.Controls.FileDialog(MmdPdf.Controls.FileDialogMode.Save)
                           { Filter = L("Str_Filter_Pdf") + "|*.pdf", Title = L("Str_Sign_SaveAs"), FileName = Path.GetFileName(_outputBox.Text) };
             if (dlg.ShowDialog(this) == true) _outputBox.Text = dlg.FileName;
         }