feat: Add Create Channel dialog and related events

- Introduced CreateChannelDialog for user to create new channels with name and topic.
- Added OnCreateChannelRequested event in MainWindow for channel creation.
- Enhanced EchoHubConnection with OnReconnected event for connection state handling.
- Updated EchoHubDbContext to use application base directory for SQLite database path.
- Integrated Serilog for logging in EchoHub.Server.
- Refactored database initialization and migration logic into DatabaseSetup class.
- Implemented FirstRunSetup to ensure appsettings.json and generate JWT secret if needed.
- Updated appsettings files to configure Serilog logging.
- Enhanced error handling and logging in ChatHub methods for better traceability.

src/EchoHub.Client/UI/CreateChannelDialog.cs

@@ -0,0 +1,77 @@
+using Terminal.Gui.App;
+using Terminal.Gui.Views;
+using Terminal.Gui.ViewBase;
+
+namespace EchoHub.Client.UI;
+
+public record CreateChannelResult(string Name, string? Topic);
+
+public sealed class CreateChannelDialog
+{
+    public static CreateChannelResult? Show(IApplication app)
+    {
+        CreateChannelResult? result = null;
+
+        var dialog = new Dialog { Title = "Create Channel", Width = 50, Height = 12 };
+
+        var nameLabel = new Label { Text = "Name:", X = 1, Y = 1 };
+        var nameField = new TextField { X = 10, Y = 1, Width = Dim.Fill(2) };
+
+        var topicLabel = new Label { Text = "Topic:", X = 1, Y = 3 };
+        var topicField = new TextField { X = 10, Y = 3, Width = Dim.Fill(2) };
+
+        var hintLabel = new Label
+        {
+            Text = "Lowercase letters, digits, hyphens, underscores (2-100 chars)",
+            X = 1,
+            Y = 5,
+        };
+
+        var createButton = new Button
+        {
+            Text = "Create",
+            IsDefault = true,
+            X = Pos.Center() - 10,
+            Y = 7
+        };
+
+        var cancelButton = new Button
+        {
+            Text = "Cancel",
+            X = Pos.Center() + 5,
+            Y = 7
+        };
+
+        createButton.Accepting += (s, e) =>
+        {
+            var name = nameField.Text?.Trim().ToLowerInvariant();
+            if (string.IsNullOrWhiteSpace(name))
+            {
+                MessageBox.ErrorQuery(app, "Error", "Channel name is required.", "OK");
+                return;
+            }
+
+            var topic = topicField.Text?.Trim();
+            if (string.IsNullOrWhiteSpace(topic))
+                topic = null;
+
+            result = new CreateChannelResult(name, topic);
+            e.Handled = true;
+            app.RequestStop();
+        };
+
+        cancelButton.Accepting += (s, e) =>
+        {
+            result = null;
+            e.Handled = true;
+            app.RequestStop();
+        };
+
+        dialog.Add(nameLabel, nameField, topicLabel, topicField, hintLabel, createButton, cancelButton);
+
+        nameField.SetFocus();
+        app.Run(dialog);
+
+        return result;
+    }
+}

src/EchoHub.Client/UI/MainWindow.cs

@@ -74,6 +74,11 @@ public sealed class MainWindow : Runnable
     /// </summary>
     public event Action? OnSavedServersRequested;
 
+    /// <summary>
+    /// Fired when the user requests to create a new channel.
+    /// </summary>
+    public event Action? OnCreateChannelRequested;
+
     public MainWindow(IApplication app)
     {
         _app = app;
@@ -228,6 +233,7 @@ public sealed class MainWindow : Runnable
                 new MenuItem("_Connect...", "Connect to a server", () => OnConnectRequested?.Invoke(), Key.Empty),
                 new MenuItem("_Disconnect", "Disconnect from server", () => OnDisconnectRequested?.Invoke(), Key.Empty),
                 new Line(),
+                new MenuItem("New C_hannel...", "Create a new channel", () => OnCreateChannelRequested?.Invoke(), Key.Empty),
                 new MenuItem("_Saved Servers...", "View saved servers", () => OnSavedServersRequested?.Invoke(), Key.Empty)
             }),
             new MenuBarItem("_User", allUserItems)