Convert Tasks module to MediatR commands/queries

Replaces ITaskService/TaskService, completing the CQRS/mediator
refactor. All 9 old service interfaces are now gone except
IPermissionService, ITokenService, and IPasswordHasher, which stay
plain injected services by design (see spec).

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

mws.api/Controllers/TasksController.cs

@@ -1,3 +1,4 @@
+using MediatR;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Mws.Application.Common;
@@ -10,12 +11,12 @@ namespace Mws.Api.Controllers;
 [ApiController]
 [Route("api")]
 [Authorize]
-public class TasksController(ITaskService taskService) : ControllerBase
+public class TasksController(ISender sender) : ControllerBase
 {
     [HttpGet("tasks/search")]
     public async Task<ActionResult<List<TaskDto>>> Search([FromQuery] string? q, CancellationToken ct)
     {
-        return Ok(await taskService.SearchAsync(User.GetUserId(), q ?? string.Empty, ct));
+        return Ok(await sender.Send(new SearchTasksQuery(User.GetUserId(), q ?? string.Empty), ct));
     }
 
     [HttpGet("projects/{projectId:guid}/tasks")]
@@ -28,32 +29,32 @@ public class TasksController(ITaskService taskService) : ControllerBase
     {
         var statusValue = ParseOptional<TaskStatus>(status);
         var priorityValue = ParseOptional<TaskPriority>(priority);
-        return Ok(await taskService.GetTasksAsync(User.GetUserId(), projectId, statusValue, priorityValue, assigneeId, ct));
+        return Ok(await sender.Send(new GetTasksQuery(User.GetUserId(), projectId, statusValue, priorityValue, assigneeId), ct));
     }
 
     [HttpPost("projects/{projectId:guid}/tasks")]
     public async Task<ActionResult<TaskDto>> Create(Guid projectId, [FromBody] CreateTaskRequest request, CancellationToken ct)
     {
-        var result = await taskService.CreateAsync(User.GetUserId(), projectId, request, ct);
+        var result = await sender.Send(new CreateTaskCommand(User.GetUserId(), projectId, request), ct);
         return CreatedAtAction(nameof(Get), new { id = result.Id }, result);
     }
 
     [HttpGet("tasks/{id:guid}")]
     public async Task<ActionResult<TaskDto>> Get(Guid id, CancellationToken ct)
     {
-        return Ok(await taskService.GetAsync(User.GetUserId(), id, ct));
+        return Ok(await sender.Send(new GetTaskQuery(User.GetUserId(), id), ct));
     }
 
     [HttpPut("tasks/{id:guid}")]
     public async Task<ActionResult<TaskDto>> Update(Guid id, [FromBody] UpdateTaskRequest request, CancellationToken ct)
     {
-        return Ok(await taskService.UpdateAsync(User.GetUserId(), id, request, ct));
+        return Ok(await sender.Send(new UpdateTaskCommand(User.GetUserId(), id, request), ct));
     }
 
     [HttpDelete("tasks/{id:guid}")]
     public async Task<IActionResult> Delete(Guid id, CancellationToken ct)
     {
-        await taskService.DeleteAsync(User.GetUserId(), id, ct);
+        await sender.Send(new DeleteTaskCommand(User.GetUserId(), id), ct);
         return NoContent();
     }
 
@@ -65,4 +66,4 @@ public class TasksController(ITaskService taskService) : ControllerBase
         }
         return Enum.TryParse<TEnum>(value, ignoreCase: true, out var result) ? result : throw new BadRequestException($"Invalid {typeof(TEnum).Name}: {value}");
     }
-}
+}