[CLAUDE] Workflow: App CQRS + API ApprovalWorkflowsV2 (Chunk B)

3 handler MediatR + Validator + Controller cho schema mới Mig 22.

Files:
- Application/ApprovalWorkflowsV2/ApprovalWorkflowV2AdminFeatures.cs
  - GetAwAdminOverviewQuery (filter optional ApplicableType)
  - CreateAwDefinitionCommand + Validator (auto-increment Version
    theo Code, deactivate active version cùng ApplicableType)
  - DeleteAwDefinitionCommand (UAT helper — chưa pin nên unconditional)
  - DTO: AwDefinition/AwStep/AwLevel + TypeSummary
- Application/Common/Interfaces/IApplicationDbContext.cs (3 DbSet)
- Api/Controllers/ApprovalWorkflowsV2Controller.cs
  - Route /api/approval-workflows-v2
  - GET ?applicableType=N | POST | DELETE/{id}
  - Reuse policy Workflows.Read/Workflows.Create

Verify: build OK 0 error, IApplicationDbContext expose 3 DbSet mới.

Next: Chunk C — FE Designer page + route + Layout resolver.

src/Backend/SolutionErp.Api/Controllers/ApprovalWorkflowsV2Controller.cs

@@ -0,0 +1,38 @@
+using MediatR;
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using SolutionErp.Application.ApprovalWorkflowsV2;
+
+namespace SolutionErp.Api.Controllers;
+
+// Quy trình duyệt MỚI (Mig 22 — Session 17, 2026-05-08).
+// Schema riêng để UAT, KHÔNG đụng WorkflowDefinition cũ.
+// Reuse policy "Workflows.Read"/"Workflows.Create" giống PE/Contract designer
+// — admin đã có quyền quản lý workflow nói chung.
+[ApiController]
+[Route("api/approval-workflows-v2")]
+[Authorize(Policy = "Workflows.Read")]
+public class ApprovalWorkflowsV2Controller(IMediator mediator) : ControllerBase
+{
+    [HttpGet]
+    public async Task<ActionResult<AwAdminOverviewDto>> Overview(
+        [FromQuery] int? applicableType,
+        CancellationToken ct)
+        => Ok(await mediator.Send(new GetAwAdminOverviewQuery(applicableType), ct));
+
+    [HttpPost]
+    [Authorize(Policy = "Workflows.Create")]
+    public async Task<ActionResult<object>> Create([FromBody] CreateAwDefinitionCommand cmd, CancellationToken ct)
+    {
+        var id = await mediator.Send(cmd, ct);
+        return Ok(new { id });
+    }
+
+    [HttpDelete("{id:guid}")]
+    [Authorize(Policy = "Workflows.Create")]
+    public async Task<IActionResult> Delete(Guid id, CancellationToken ct)
+    {
+        await mediator.Send(new DeleteAwDefinitionCommand(id), ct);
+        return NoContent();
+    }
+}