refactor(P0): CPM 도입 + Magick.NET 14.13.1 통일

- src/Directory.Packages.props 신규 — 모든 PackageReference 버전의 단일 출처(SSOT)
- ManagePackageVersionsCentrally=true, 3개 csproj에서 Version 속성 제거
- Magick.NET-Q16-AnyCPU Core 14.13.0 → 14.13.1로 통일(Tests와 정합)
  테스트와 프로덕션이 동일 네이티브 바이너리로 동작 → 골든마스터 신뢰 기반 확보

빌드 0경고/0오류, 38개 테스트 전부 그린.

src/Everything2Everything.Core/Everything2Everything.Core.csproj

@@ -12,20 +12,20 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="ClosedXML" Version="0.105.0" />
-    <PackageReference Include="CsvHelper" Version="33.1.0" />
-    <PackageReference Include="FFMpegCore" Version="5.4.0" />
-    <PackageReference Include="Magick.NET-Q16-AnyCPU" Version="14.13.0" />
-    <PackageReference Include="PDFtoImage" Version="5.2.1" />
-    <PackageReference Include="PhotoSauce.MagicScaler" Version="0.15.0" />
-    <PackageReference Include="PhotoSauce.NativeCodecs.Libheif" Version="1.19.5-preview1" />
-    <PackageReference Include="Microsoft.Web.WebView2" Version="1.0.3912.50" />
-    <PackageReference Include="DocumentFormat.OpenXml" Version="3.5.1" />
-    <PackageReference Include="Markdig" Version="0.37.0" />
-    <PackageReference Include="ReverseMarkdown" Version="4.6.0" />
-    <PackageReference Include="PDFsharp" Version="6.2.0" />
-    <PackageReference Include="Svg.Skia" Version="5.0.0" />
-    <PackageReference Include="System.Security.Cryptography.ProtectedData" Version="10.0.8" />
+    <PackageReference Include="ClosedXML" />
+    <PackageReference Include="CsvHelper" />
+    <PackageReference Include="FFMpegCore" />
+    <PackageReference Include="Magick.NET-Q16-AnyCPU" />
+    <PackageReference Include="PDFtoImage" />
+    <PackageReference Include="PhotoSauce.MagicScaler" />
+    <PackageReference Include="PhotoSauce.NativeCodecs.Libheif" />
+    <PackageReference Include="Microsoft.Web.WebView2" />
+    <PackageReference Include="DocumentFormat.OpenXml" />
+    <PackageReference Include="Markdig" />
+    <PackageReference Include="ReverseMarkdown" />
+    <PackageReference Include="PDFsharp" />
+    <PackageReference Include="Svg.Skia" />
+    <PackageReference Include="System.Security.Cryptography.ProtectedData" />
   </ItemGroup>
 
   <ItemGroup>