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.

Shell/RailFlyouts.cs

@@ -3,7 +3,7 @@ using System.Windows;
 using System.Windows.Controls;
 using System.Windows.Media.Animation;
 
-namespace KillerPDF
+namespace MmdPdf
 {
     /// <summary>
     /// The rail's flyout buttons (family order, locked 2026-07-30: app-specific toggles, then
@@ -20,7 +20,6 @@ namespace KillerPDF
 
         private void RailLang_Click(object sender, RoutedEventArgs e) => ToggleRailFlyout(LangFlyout);
 
-        private void RailTheme_Click(object sender, RoutedEventArgs e) => ToggleRailFlyout(ThemeFlyout);
 
         private void RailView_Click(object sender, RoutedEventArgs e) => ToggleRailFlyout(ViewFlyout);
 
@@ -49,14 +48,14 @@ namespace KillerPDF
             SyncPickerState();
         }
 
+
+
         private void ToggleRailFlyout(ContextMenu menu)
         {
             if (menu.IsOpen) { menu.IsOpen = false; return; }
 
             // The theme strip always faces the document. Mirroring the two columns also makes its
             // width animation grow outward from the rail on either side of the window.
-            if (menu == ThemeFlyout)
-                SyncThemeFlyoutSide();
 
             // Radios and accent dots reflect live state before the card shows - the same single
             // sync the Settings panel runs on open.
@@ -79,24 +78,5 @@ namespace KillerPDF
                     EasingFunction = new QuadraticEase { EasingMode = EasingMode.EaseOut }
                 });
         }
-
-        private void SyncThemeFlyoutSide()
-        {
-            if (ThemePickerLayout is null || ThemeSubmenu is null || AccentStripHost is null ||
-                AccentStripDivider is null || AccentStrip is null)
-                return;
-
-            Grid.SetColumn(ThemeSubmenu, _sidebarRight ? 1 : 0);
-            Grid.SetColumn(AccentStripHost, _sidebarRight ? 0 : 1);
-            AccentStripDivider.HorizontalAlignment = _sidebarRight
-                ? HorizontalAlignment.Right
-                : HorizontalAlignment.Left;
-            AccentStrip.Margin = _sidebarRight
-                ? new Thickness(2, 6, 7, 6)
-                : new Thickness(7, 6, 2, 6);
-            ThemePickerLayout.Margin = _sidebarRight
-                ? new Thickness(3, 10, 12, 10)
-                : new Thickness(12, 10, 3, 10);
-        }
     }
 }