Remove ARG APP_UID and set it as ENV

RackPeek.Web/Dockerfile

@@ -3,7 +3,6 @@
 # -----------------------------
 FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS base
 
-ARG APP_UID=1000
 ENV APP_UID=$APP_UID
 
 WORKDIR /app
@@ -69,4 +68,4 @@ ENV RPK_YAML_DIR=/app/config
 # Drop privileges
 USER ${APP_UID}
 
-ENTRYPOINT ["dotnet", "RackPeek.Web.dll"]
+ENTRYPOINT ["dotnet", "RackPeek.Web.dll"]