feat: Refactor authentication and token management

- Updated EchoHubConnection to use ApiClient for token retrieval.
- Introduced ValidationConstants for common validation patterns and limits.
- Enhanced AuthDtos with refresh token support and expiration details.
- Added new ChatDtos for channel creation and topic updates.
- Created CommonDtos for error and paginated responses.
- Implemented RefreshToken model for managing refresh tokens.
- Modified JwtTokenService to generate and hash refresh tokens.
- Updated AuthController to handle registration, login, token refresh, and logout with improved error handling.
- Enhanced ChannelsController with channel creation, topic updates, and pagination for channel retrieval.
- Added FilesController for file management with rate limiting.
- Improved UsersController for profile updates and avatar uploads with validation.
- Integrated rate limiting across controllers to manage request load.
- Introduced FileValidationHelper for validating uploaded image files.
- Updated database context to include RefreshToken and enforce unique constraints.
- Enhanced ChatHub for improved channel and message handling with validation.
- Updated Program.cs to configure rate limiting and CORS policies.

src/EchoHub.Core/DTOs/AuthDtos.cs

@@ -4,4 +4,12 @@ public record RegisterRequest(string Username, string Password, string? DisplayN
 
 public record LoginRequest(string Username, string Password);
 
-public record LoginResponse(string Token, string Username, string? DisplayName, string? NicknameColor);
+public record LoginResponse(
+    string Token,
+    string RefreshToken,
+    DateTimeOffset ExpiresAt,
+    string Username,
+    string? DisplayName,
+    string? NicknameColor);
+
+public record RefreshRequest(string RefreshToken);

src/EchoHub.Core/DTOs/ChatDtos.cs

@@ -29,3 +29,7 @@ public record UserDto(
     DateTimeOffset LastSeenAt);
 
 public record SendMessageRequest(string ChannelName, string Content);
+
+public record CreateChannelRequest(string Name, string? Topic = null);
+
+public record UpdateTopicRequest(string? Topic);

src/EchoHub.Core/DTOs/CommonDtos.cs

@@ -0,0 +1,5 @@
+namespace EchoHub.Core.DTOs;
+
+public record ErrorResponse(string Error, string? Detail = null);
+
+public record PaginatedResponse<T>(List<T> Items, int Total, int Offset, int Limit);

src/EchoHub.Core/DTOs/ProfileDtos.cs

@@ -29,3 +29,5 @@ public record UserPresenceDto(
     string? NicknameColor,
     UserStatus Status,
     string? StatusMessage);
+
+public record AvatarUploadResponse(string AvatarAscii);