chore(docker): rely on the aspnet image's port setting

mcr.microsoft.com/dotnet/aspnet:10.0-noble already sets ASPNETCORE_HTTP_PORTS=8080;
also setting ASPNETCORE_URLS made Kestrel log an override warning on every start.

Dockerfile

@@ -81,8 +81,7 @@ ENV Telegram__WorkspaceRoot=/data/workspaces \
     DOTNET_CLI_TELEMETRY_OPTOUT=1 \
     DOTNET_NOLOGO=1 \
     TZ=UTC \
-    DOTNET_EnableDiagnostics=0 \
-    ASPNETCORE_URLS=http://+:8080
+    DOTNET_EnableDiagnostics=0
 
 # The A2A server (A2A__Enabled=true); with A2A off the bot opens no port at all.
 EXPOSE 8080