Convert ProjectMembers module to MediatR commands/queries

Replaces IProjectMemberService/ProjectMemberService, completing the
Projects module conversion.

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

mws.api/Controllers/ProjectMembersController.cs

@@ -1,3 +1,4 @@
+using MediatR;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Mws.Application.Projects;
@@ -7,31 +8,31 @@ namespace Mws.Api.Controllers;
 [ApiController]
 [Route("api/projects/{projectId:guid}/members")]
 [Authorize]
-public class ProjectMembersController(IProjectMemberService memberService) : ControllerBase
+public class ProjectMembersController(ISender sender) : ControllerBase
 {
     [HttpGet]
     public async Task<ActionResult<List<ProjectMemberDto>>> GetAll(Guid projectId, CancellationToken ct)
     {
-        return Ok(await memberService.GetMembersAsync(User.GetUserId(), projectId, ct));
+        return Ok(await sender.Send(new GetProjectMembersQuery(User.GetUserId(), projectId), ct));
     }
 
     [HttpPost]
     public async Task<ActionResult<ProjectMemberDto>> Add(Guid projectId, [FromBody] AddMemberRequest request, CancellationToken ct)
     {
-        return Ok(await memberService.AddMemberAsync(User.GetUserId(), projectId, request, ct));
+        return Ok(await sender.Send(new AddProjectMemberCommand(User.GetUserId(), projectId, request), ct));
     }
 
     [HttpPut("{userId:guid}/document-permissions")]
     public async Task<ActionResult<ProjectMemberDto>> UpdateDocumentPermissions(
         Guid projectId, Guid userId, [FromBody] UpdateMemberDocumentPermissionsRequest request, CancellationToken ct)
     {
-        return Ok(await memberService.UpdateMemberDocumentPermissionsAsync(User.GetUserId(), projectId, userId, request, ct));
+        return Ok(await sender.Send(new UpdateMemberDocumentPermissionsCommand(User.GetUserId(), projectId, userId, request), ct));
     }
 
     [HttpDelete("{userId:guid}")]
     public async Task<IActionResult> Remove(Guid projectId, Guid userId, CancellationToken ct)
     {
-        await memberService.RemoveMemberAsync(User.GetUserId(), projectId, userId, ct);
+        await sender.Send(new RemoveProjectMemberCommand(User.GetUserId(), projectId, userId), ct);
         return NoContent();
     }
-}
+}