Convert Accounts module to MediatR commands/queries

Replaces IAccountService/AccountService with one command/query per
operation, following the pattern set in the Auth module.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

mws.application/Accounts/Commands/ResetPassword.cs

@@ -0,0 +1,31 @@
+using MediatR;
+using Mws.Application.Auth;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+
+namespace Mws.Application.Accounts;
+
+public record ResetPasswordCommand(Guid ActorUserId, Guid Id, ResetPasswordRequest Request) : IRequest;
+
+public class ResetPasswordHandler(IUnitOfWork uow, IPasswordHasher passwordHasher, IPermissionService permissions)
+    : IRequestHandler<ResetPasswordCommand>
+{
+    private const string Screen = "accounts";
+
+    public async Task Handle(ResetPasswordCommand command, CancellationToken ct)
+    {
+        await permissions.EnsureAsync(command.ActorUserId, Screen, PermissionAction.Edit, ct);
+
+        if (string.IsNullOrWhiteSpace(command.Request.NewPassword))
+        {
+            throw new BadRequestException("New password is required");
+        }
+
+        var user = await uow.Users.GetByIdAsync(command.Id, ct)
+            ?? throw new NotFoundException("Account not found");
+
+        user.PasswordHash = passwordHasher.Hash(command.Request.NewPassword);
+        user.UpdatedAt = DateTime.UtcNow;
+        await uow.SaveChangesAsync(ct);
+    }
+}