feat(backend): generic settings RPC bridge, LogStreamHub SignalR, and log ringbuffer

FinlyticBackend/Program.cs

@@ -191,6 +191,10 @@ app.MapHub<FavoritesPriceHub>("/hubs/favorites-prices", options =>
 {
     options.Transports = HttpTransportType.WebSockets | HttpTransportType.ServerSentEvents;
 });
+app.MapHub<LogStreamHub>("/hubs/logs", options =>
+{
+    options.Transports = HttpTransportType.WebSockets | HttpTransportType.ServerSentEvents;
+});
 
 app.MapGet("/health", () => Results.Ok(new { status = "Healthy", service = "FinlyticBackend", timestamp = DateTime.UtcNow }));