Add user authentication and account management system

Features:
- User registration with username, email, password
- Login with JWT token authentication
- Password hashing with BCrypt
- Account settings & management
- Device linking to accounts
- Change password & password reset
- Account-User relationship (1-to-1 with game data)

Database entities:
- Account: User accounts with credentials
- DeviceAccount: Link devices to accounts (many-to-many)

API endpoints:
- POST /api/auth/register
- POST /api/auth/login
- POST /api/auth/change-password
- POST /api/auth/forgot-password
- POST /api/auth/reset-password
- GET /api/auth/me
- POST /api/auth/link-device
- DELETE /api/auth/unlink-device/{deviceId}

Starting resources for new accounts:
- 100,000 Gold
- 500,000 Cash
- Level 1

Ready for VPS deployment with HTTPS.

RR3CommunityServer/Models/AccountModels.cs

@@ -0,0 +1,113 @@
+using RR3CommunityServer.Data;
+
+namespace RR3CommunityServer.Models;
+
+// Account entity with authentication
+public class Account
+{
+    public int Id { get; set; }
+    public string Username { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public string PasswordHash { get; set; } = string.Empty;
+    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+    public DateTime? LastLoginAt { get; set; }
+    public bool IsActive { get; set; } = true;
+    public bool EmailVerified { get; set; } = false;
+    public string? EmailVerificationToken { get; set; }
+    public string? PasswordResetToken { get; set; }
+    public DateTime? PasswordResetExpiry { get; set; }
+    
+    // Link to game user data
+    public int? UserId { get; set; }
+    public User? User { get; set; }
+    
+    // Multiple devices can be linked to one account
+    public List<DeviceAccount> LinkedDevices { get; set; } = new();
+}
+
+// Join table for account-device relationship
+public class DeviceAccount
+{
+    public int Id { get; set; }
+    public int AccountId { get; set; }
+    public Account Account { get; set; } = null!;
+    public string DeviceId { get; set; } = string.Empty;
+    public string? DeviceName { get; set; }
+    public DateTime LinkedAt { get; set; } = DateTime.UtcNow;
+    public DateTime LastUsedAt { get; set; } = DateTime.UtcNow;
+}
+
+// Request/Response DTOs for authentication
+public class RegisterRequest
+{
+    public string Username { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public string Password { get; set; } = string.Empty;
+    public string ConfirmPassword { get; set; } = string.Empty;
+}
+
+public class LoginRequest
+{
+    public string UsernameOrEmail { get; set; } = string.Empty;
+    public string Password { get; set; } = string.Empty;
+    public string? DeviceId { get; set; }
+}
+
+public class LoginResponse
+{
+    public string Token { get; set; } = string.Empty;
+    public int AccountId { get; set; }
+    public string Username { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public DateTime ExpiresAt { get; set; }
+}
+
+public class ChangePasswordRequest
+{
+    public string CurrentPassword { get; set; } = string.Empty;
+    public string NewPassword { get; set; } = string.Empty;
+    public string ConfirmPassword { get; set; } = string.Empty;
+}
+
+public class ForgotPasswordRequest
+{
+    public string Email { get; set; } = string.Empty;
+}
+
+public class ResetPasswordRequest
+{
+    public string Token { get; set; } = string.Empty;
+    public string NewPassword { get; set; } = string.Empty;
+    public string ConfirmPassword { get; set; } = string.Empty;
+}
+
+public class LinkDeviceRequest
+{
+    public string DeviceId { get; set; } = string.Empty;
+    public string? DeviceName { get; set; }
+}
+
+public class AccountSettingsResponse
+{
+    public int AccountId { get; set; }
+    public string Username { get; set; } = string.Empty;
+    public string Email { get; set; } = string.Empty;
+    public bool EmailVerified { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime? LastLoginAt { get; set; }
+    public List<LinkedDeviceInfo> LinkedDevices { get; set; } = new();
+    
+    // Game progress
+    public int? Gold { get; set; }
+    public int? Cash { get; set; }
+    public int? Level { get; set; }
+    public int? CarsOwned { get; set; }
+}
+
+public class LinkedDeviceInfo
+{
+    public string DeviceId { get; set; } = string.Empty;
+    public string? DeviceName { get; set; }
+    public DateTime LinkedAt { get; set; }
+    public DateTime LastUsedAt { get; set; }
+}