v3.9.1: plain/WASAPI streams now play on an ASIO-mode receiver (silent-mic fix)

Receiver: a Mixed (plain) session is rendered on an active lane in BothIndependent mode instead of being skipped, so a WASAPI-only sender is no longer silent to a receiver that has an ASIO driver selected. Also port the per-session buffer depth-drain (stops the receive jitter buffer bloating).

Sender: add sndAudFr meter (audio frames actually sent) to localise capture vs send.

App: startup sound cue (machine-wide, Preferences); stop sending audio when no peer is reachable (issue #8). Version 3.9.1.

Server (relay): fix updater version-compare for multi-dot tags, guard the main loop against crashes, reject spoofed BYE from a mismatched endpoint.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/RemSound.App.csproj

@@ -14,7 +14,7 @@
          tag_name on the latest GitHub release; bump it on every public release. The
          AssemblyVersion / FileVersion default to this value, and Assembly.GetName().Version
          is what the About dialog and the updater both read. -->
-    <Version>3.8.0</Version>
+    <Version>3.9.1</Version>
   </PropertyGroup>
 
   <ItemGroup>
@@ -103,6 +103,13 @@
       <Link>sounds\profile menu open.wav</Link>
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <!-- start up.wav (v3.9): plays once when RemSound starts, right after this copy wins the
+         single-instance takeover and before the profile loads. Machine-wide enable + custom
+         override (AppConfig), since it fires before any profile is chosen. -->
+    <Content Include="..\..\sounds\start up.wav" Condition="Exists('..\..\sounds\start up.wav')">
+      <Link>sounds\start up.wav</Link>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
     <!-- User manual. F1 anywhere in the app opens this via the user's default browser
          (HelpLauncher.OpenManual). The PreserveNewest mode means a fresh publish overwrites
          the published copy whenever the source is newer; manually-edited copies inside