Add core models, DTOs, and services for EchoHub chat application

- Created User, Channel, Message, and ServerInfo models with necessary properties.
- Added DTOs for user profiles, server information, and message handling.
- Implemented JWT authentication service for user login and token generation.
- Developed Entity Framework Core DbContext for database interactions.
- Introduced SignalR ChatHub for real-time messaging and presence tracking.
- Implemented file storage and image to ASCII conversion services.
- Set up CORS and middleware for API endpoints.
- Created launch settings and development configuration for server and web projects.

src/EchoHub.Client/Config/ClientConfig.cs

@@ -0,0 +1,24 @@
+namespace EchoHub.Client.Config;
+
+public class ClientConfig
+{
+    public List<SavedServer> SavedServers { get; set; } = [];
+    public AccountPreset DefaultPreset { get; set; } = new();
+    public string ActiveTheme { get; set; } = "Default";
+}
+
+public class SavedServer
+{
+    public required string Name { get; set; }
+    public required string Url { get; set; }
+    public string? Username { get; set; }
+    public string? Token { get; set; }
+    public DateTimeOffset LastConnected { get; set; }
+}
+
+public class AccountPreset
+{
+    public string? DisplayName { get; set; }
+    public string? Bio { get; set; }
+    public string? NicknameColor { get; set; }
+}