Fix large CMS upload timeout with idle heartbeat and add per-file progress meter

Replace the 100s default HttpClient timeout (set Timeout=Infinite) with an idle/heartbeat
deadline driven by a ProgressStreamContent wrapper that reports bytes-on-the-wire. Each tick
resets the idle window and advances a MudProgressLinear per upload row. Idle window is
configurable via Upload:IdleTimeoutSeconds (default 90s).

DeepDrftManager/Program.cs

@@ -52,6 +52,10 @@ builder.Services.AddHttpClient("DeepDrft.Content.Cms", client =>
 {
     client.BaseAddress = new Uri(contentApiUrl);
     client.DefaultRequestHeaders.Add("ApiKey", contentApiKey);
+    // Large mix uploads (several hundred MB) outrun the 100s default whole-request timeout. The send
+    // path enforces an idle/heartbeat deadline instead (CmsTrackService), which can only express
+    // "no bytes for N seconds" if the client itself does not impose a total cap — hence Infinite here.
+    client.Timeout = Timeout.InfiniteTimeSpan;
 });
 
 // Reverse-proxy support (nginx in production).