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; }
+}

src/EchoHub.Client/Config/ConfigManager.cs

@@ -0,0 +1,70 @@
+using System.Text.Json;
+
+namespace EchoHub.Client.Config;
+
+public static class ConfigManager
+{
+    private static readonly string ConfigDir = Path.Combine(
+        Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".echohub");
+
+    private static readonly string ConfigPath = Path.Combine(ConfigDir, "config.json");
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        WriteIndented = true,
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+    };
+
+    public static ClientConfig Load()
+    {
+        try
+        {
+            if (!File.Exists(ConfigPath))
+                return new ClientConfig();
+
+            var json = File.ReadAllText(ConfigPath);
+            return JsonSerializer.Deserialize<ClientConfig>(json, JsonOptions) ?? new ClientConfig();
+        }
+        catch
+        {
+            return new ClientConfig();
+        }
+    }
+
+    public static void Save(ClientConfig config)
+    {
+        try
+        {
+            Directory.CreateDirectory(ConfigDir);
+            var json = JsonSerializer.Serialize(config, JsonOptions);
+            File.WriteAllText(ConfigPath, json);
+        }
+        catch
+        {
+            // Silently fail — config save is best-effort
+        }
+    }
+
+    public static void SaveServer(SavedServer server)
+    {
+        var config = Load();
+        var existing = config.SavedServers.FindIndex(s =>
+            string.Equals(s.Url, server.Url, StringComparison.OrdinalIgnoreCase));
+
+        if (existing >= 0)
+            config.SavedServers[existing] = server;
+        else
+            config.SavedServers.Add(server);
+
+        Save(config);
+    }
+
+    public static void RemoveServer(string url)
+    {
+        var config = Load();
+        config.SavedServers.RemoveAll(s =>
+            string.Equals(s.Url, url, StringComparison.OrdinalIgnoreCase));
+
+        Save(config);
+    }
+}