mbproxy: embed debug symbols in the RID publish, drop the loose .pdb

A Release publish with an explicit RID emitted a separate Mbproxy.pdb
alongside the single-file binary. Set DebugType=embedded for that
publish so the output folder is just the binary plus appsettings.json;
symbols stay available for exception stack traces, only the loose file
is gone. A plain RID-less build is unaffected.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mbproxy/src/Mbproxy/Mbproxy.csproj

@@ -26,6 +26,10 @@
     <PublishSingleFile>true</PublishSingleFile>
     <SelfContained>true</SelfContained>
     <IncludeNativeLibrariesForSelfExtract>true</IncludeNativeLibrariesForSelfExtract>
+    <!-- Embed debug symbols into the assembly instead of emitting a loose .pdb, so a
+         RID publish produces a clean folder (single binary + appsettings.json). Symbols
+         stay available for exception stack traces; there is just no separate file. -->
+    <DebugType>embedded</DebugType>
   </PropertyGroup>
 
   <ItemGroup>