Add SignalR integration for real-time weather updates

Implemented SignalR to enable real-time communication between the server and connected clients. Added a new hub (`WeatherUpdateHub`), a background service (`SignalRSendService`), and modified both the API backend and React frontend for seamless message broadcasting and handling.

Api/SignalR/SignalRSendService.cs

@@ -0,0 +1,31 @@
+using Microsoft.AspNetCore.SignalR;
+
+namespace Api.SignalR
+{
+    public class SignalRSendService(IHubContext<WeatherUpdateHub> hubContext, ILogger<SignalRSendService> logger) : BackgroundService
+    {
+        
+        #region Override ExecuteAsync
+
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                // For example, wait 10 seconds between messages.
+                await Task.Delay(TimeSpan.FromSeconds(10), stoppingToken);
+
+                // Log or do any work here.
+                logger.LogInformation("Background service sending message at: {Time}", DateTime.Now);
+
+                // Send a message to all connected clients.
+                await hubContext.Clients.All.SendAsync(
+                    "ReceiveMessage", // This is the client method name.
+                    "Background Service", // Example sender.
+                    "Hello from the background task!", // The message.
+                    stoppingToken);
+            }
+        }
+
+        #endregion
+    }
+}