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/Queries/GetAccounts.cs

@@ -0,0 +1,22 @@
+using AutoMapper;
+using MediatR;
+using Mws.Application.Common;
+using Mws.Application.Permissions;
+
+namespace Mws.Application.Accounts;
+
+public record GetAccountsQuery(Guid ActorUserId, string? Term) : IRequest<List<AccountDto>>;
+
+public class GetAccountsHandler(IUnitOfWork uow, IPermissionService permissions, IMapper mapper)
+    : IRequestHandler<GetAccountsQuery, List<AccountDto>>
+{
+    private const string Screen = "accounts";
+
+    public async Task<List<AccountDto>> Handle(GetAccountsQuery query, CancellationToken ct)
+    {
+        await permissions.EnsureAsync(query.ActorUserId, Screen, PermissionAction.View, ct);
+
+        var users = await uow.Users.SearchWithRoleAsync(query.Term, null, ct);
+        return mapper.Map<List<AccountDto>>(users);
+    }
+}