Add real-time dashboard updates with SignalR

Integrate SignalR to provide real-time dashboard update notifications.
- Added DashboardsHub and DashboardChangeNotifier on the backend.
- Modified SqlDashboardStorage to trigger notifications on changes.
- Registered SignalR services and mapped the hub endpoint.
- Updated Blazor clients to connect to the hub and refresh dashboards on change.
- Added SignalR client packages and necessary DI/configuration.

DbFirst.API/Dashboards/DashboardChangeNotifier.cs

@@ -0,0 +1,19 @@
+using DbFirst.API.Hubs;
+using Microsoft.AspNetCore.SignalR;
+
+namespace DbFirst.API.Dashboards;
+
+public class DashboardChangeNotifier : IDashboardChangeNotifier
+{
+    private readonly IHubContext<DashboardsHub> _hubContext;
+
+    public DashboardChangeNotifier(IHubContext<DashboardsHub> hubContext)
+    {
+        _hubContext = hubContext;
+    }
+
+    public void NotifyChanged()
+    {
+        _ = _hubContext.Clients.All.SendAsync("DashboardsChanged");
+    }
+}

DbFirst.API/Dashboards/IDashboardChangeNotifier.cs

@@ -0,0 +1,6 @@
+namespace DbFirst.API.Dashboards;
+
+public interface IDashboardChangeNotifier
+{
+    void NotifyChanged();
+}

DbFirst.API/Dashboards/SqlDashboardStorage.cs

@@ -11,12 +11,14 @@ public sealed class SqlDashboardStorage : IEditableDashboardStorage
     private readonly string _connectionString;
     private readonly string _tableName;
     private readonly Func<string?>? _userProvider;
+    private readonly IDashboardChangeNotifier? _notifier;
 
-    public SqlDashboardStorage(string connectionString, string tableName = "TBDD_SMF_CONFIG", Func<string?>? userProvider = null)
+    public SqlDashboardStorage(string connectionString, string tableName = "TBDD_SMF_CONFIG", Func<string?>? userProvider = null, IDashboardChangeNotifier? notifier = null)
     {
         _connectionString = connectionString;
         _tableName = tableName;
         _userProvider = userProvider;
+        _notifier = notifier;
     }
 
     public IEnumerable<DashboardInfo> GetAvailableDashboardsInfo()
@@ -98,6 +100,7 @@ public sealed class SqlDashboardStorage : IEditableDashboardStorage
 
         connection.Open();
         command.ExecuteNonQuery();
+        _notifier?.NotifyChanged();
         return id;
     }
 
@@ -118,6 +121,8 @@ public sealed class SqlDashboardStorage : IEditableDashboardStorage
         {
             throw new ArgumentException($"Dashboard '{dashboardId}' not found.");
         }
+
+        _notifier?.NotifyChanged();
     }
 
     public void DeleteDashboard(string dashboardId)
@@ -128,5 +133,6 @@ public sealed class SqlDashboardStorage : IEditableDashboardStorage
 
         connection.Open();
         command.ExecuteNonQuery();
+        _notifier?.NotifyChanged();
     }
 }