feat: print build info at startup; version placeholders filled in by CI [CI SKIP]

backend/probe/src/MoShiro.Probe/ProbeApp.cs

@@ -103,6 +103,7 @@ public sealed class ProbeApp : IDisposable
 
     public async Task RunAsync(CancellationToken ct)
     {
+        _log.Info("moshiro probe starting", MoShiro.Protocol.BuildInfo.Fields);
         if (_env.Directory.Agents.Count == 0)
         {
             _log.Info("no agents known yet, waiting for the panel to send the list");