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.

MmdPdf.sln

@@ -0,0 +1,31 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.14.37027.9 d17.14
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "MmdPdf", "MmdPdf.csproj", "{D7AFAEB6-1B7F-41FB-86C5-A5B17169D42F}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PdfSharpCore", "third_party\PdfSharpCore\PdfSharpCore.csproj", "{4C8A9D31-52E6-4B7A-9F0D-2A6E8B1C7D45}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{D7AFAEB6-1B7F-41FB-86C5-A5B17169D42F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D7AFAEB6-1B7F-41FB-86C5-A5B17169D42F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D7AFAEB6-1B7F-41FB-86C5-A5B17169D42F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D7AFAEB6-1B7F-41FB-86C5-A5B17169D42F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{4C8A9D31-52E6-4B7A-9F0D-2A6E8B1C7D45}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{4C8A9D31-52E6-4B7A-9F0D-2A6E8B1C7D45}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{4C8A9D31-52E6-4B7A-9F0D-2A6E8B1C7D45}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{4C8A9D31-52E6-4B7A-9F0D-2A6E8B1C7D45}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {45DCC74D-BB06-4D90-8EEE-8FDE7B8AB84E}
+	EndGlobalSection
+EndGlobal