Convert Auth module to MediatR command

Adds the MediatR package and wires AddMediatR in DI. Replaces
IAuthService/AuthService with LoginCommand/LoginHandler, the pattern
the remaining modules will follow.

mws.application/Auth/AuthService.cs

@@ -1,35 +0,0 @@
-using AutoMapper;
-using Mws.Application.Common;
-
-namespace Mws.Application.Auth;
-
-public interface IAuthService
-{
-    Task<LoginResponse> LoginAsync(LoginRequest request, CancellationToken cancellationToken = default);
-}
-
-public class AuthService(IUnitOfWork uow, IPasswordHasher passwordHasher, ITokenService tokenService, IMapper mapper)
-    : IAuthService
-{
-    public async Task<LoginResponse> LoginAsync(LoginRequest request, CancellationToken cancellationToken = default)
-    {
-        var username = request.Username.Trim();
-        var user = await uow.Users.GetByUsernameWithRoleAsync(username, cancellationToken);
-
-        if (user is null || !passwordHasher.Verify(request.Password, user.PasswordHash))
-        {
-            throw new UnauthorizedException("Invalid username or password");
-        }
-
-        if (!user.IsActive)
-        {
-            throw new ForbiddenException("Account disabled");
-        }
-
-        return new LoginResponse
-        {
-            Token = tokenService.CreateToken(user.Id, user.Username),
-            User = mapper.Map<UserDto>(user),
-        };
-    }
-}

mws.application/Auth/Commands/Login.cs

@@ -0,0 +1,33 @@
+using AutoMapper;
+using MediatR;
+using Mws.Application.Common;
+
+namespace Mws.Application.Auth;
+
+public record LoginCommand(LoginRequest Request) : IRequest<LoginResponse>;
+
+public class LoginHandler(IUnitOfWork uow, IPasswordHasher passwordHasher, ITokenService tokenService, IMapper mapper)
+    : IRequestHandler<LoginCommand, LoginResponse>
+{
+    public async Task<LoginResponse> Handle(LoginCommand command, CancellationToken ct)
+    {
+        var username = command.Request.Username.Trim();
+        var user = await uow.Users.GetByUsernameWithRoleAsync(username, ct);
+
+        if (user is null || !passwordHasher.Verify(command.Request.Password, user.PasswordHash))
+        {
+            throw new UnauthorizedException("Invalid username or password");
+        }
+
+        if (!user.IsActive)
+        {
+            throw new ForbiddenException("Account disabled");
+        }
+
+        return new LoginResponse
+        {
+            Token = tokenService.CreateToken(user.Id, user.Username),
+            User = mapper.Map<UserDto>(user),
+        };
+    }
+}

mws.application/mws.application.csproj

@@ -12,6 +12,7 @@
 
     <ItemGroup>
       <PackageReference Include="AutoMapper" Version="16.2.0" />
+      <PackageReference Include="MediatR" Version="14.2.0" />
     </ItemGroup>
 
 </Project>