[CLAUDE] App+Api: 7 Details CRUD endpoints + Changelogs query

## DTOs (Application/Contracts/Dtos/ContractDetailDtos.cs)

- 7 typed DTOs (ThauPhuDetailDto, GiaoKhoanDetailDto, NhaCungCapDetailDto,
  DichVuDetailDto, MuaBanDetailDto, NguyenTacNccDetailDto,
  NguyenTacDvDetailDto) — schema 1-1 với Domain entities
- ContractDetailsBundleDto — wrapper trả về theo Type, chỉ 1 list có data
  (FE đọc field tương ứng, tránh polymorphic deserialize phức tạp)
- ContractChangelogDto — full audit entry

## CQRS (Application/Contracts/ContractDetailsFeatures.cs)

- GetContractDetailsQuery — load bundle, switch theo Contract.Type chỉ
  query bảng tương ứng (avoid 7 query waste)
- 7 AddXxxDetailCommand handlers — typed payload + EnsureContractType
  guard (throw ConflictException nếu Contract.Type sai)
- DeleteContractDetailCommand generic — dispatch xóa theo Type, log change
- Tất cả handler call IChangelogService.LogDetailChangeAsync với summary
  human-readable (vd "Thêm hạng mục: Đào móng")

## CQRS (Application/Contracts/ContractChangelogFeatures.cs)

- ListContractChangelogsQuery (read-only) — desc CreatedAt, default top 200

## Controller (Api/Controllers/ContractsController.cs)

8 endpoints mới:
- GET /api/contracts/{id}/details → bundle theo Type
- POST /api/contracts/{id}/details/{thau-phu|giao-khoan|nha-cung-cap|
  dich-vu|mua-ban|nguyen-tac-ncc|nguyen-tac-dv} → 7 typed POST
- DELETE /api/contracts/{id}/details/{detailId} → generic delete
- GET /api/contracts/{id}/changelogs → list audit entries

Build: dotnet pass (0 error)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -101,6 +101,74 @@ public class ContractsController(IMediator mediator) : ControllerBase
         await mediator.Send(new DeleteContractAttachmentCommand(id, attId), ct);
         return NoContent();
     }
+
+    // ========== Details (per ContractType) ==========
+
+    [HttpGet("{id:guid}/details")]
+    public async Task<ContractDetailsBundleDto> GetDetails(Guid id, CancellationToken ct)
+        => await mediator.Send(new GetContractDetailsQuery(id), ct);
+
+    [HttpPost("{id:guid}/details/thau-phu")]
+    public async Task<IActionResult> AddThauPhuDetail(Guid id, [FromBody] ThauPhuDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddThauPhuDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/giao-khoan")]
+    public async Task<IActionResult> AddGiaoKhoanDetail(Guid id, [FromBody] GiaoKhoanDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddGiaoKhoanDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/nha-cung-cap")]
+    public async Task<IActionResult> AddNhaCungCapDetail(Guid id, [FromBody] NhaCungCapDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddNhaCungCapDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/dich-vu")]
+    public async Task<IActionResult> AddDichVuDetail(Guid id, [FromBody] DichVuDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddDichVuDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/mua-ban")]
+    public async Task<IActionResult> AddMuaBanDetail(Guid id, [FromBody] MuaBanDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddMuaBanDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/nguyen-tac-ncc")]
+    public async Task<IActionResult> AddNguyenTacNccDetail(Guid id, [FromBody] NguyenTacNccDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddNguyenTacNccDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpPost("{id:guid}/details/nguyen-tac-dv")]
+    public async Task<IActionResult> AddNguyenTacDvDetail(Guid id, [FromBody] NguyenTacDvDetailDto body, CancellationToken ct)
+    {
+        var newId = await mediator.Send(new AddNguyenTacDvDetailCommand(id, body), ct);
+        return CreatedAtAction(nameof(GetDetails), new { id }, new { id = newId });
+    }
+
+    [HttpDelete("{id:guid}/details/{detailId:guid}")]
+    public async Task<IActionResult> DeleteDetail(Guid id, Guid detailId, CancellationToken ct)
+    {
+        await mediator.Send(new DeleteContractDetailCommand(id, detailId), ct);
+        return NoContent();
+    }
+
+    // ========== Changelogs (read-only) ==========
+
+    [HttpGet("{id:guid}/changelogs")]
+    public async Task<List<ContractChangelogDto>> GetChangelogs(Guid id, CancellationToken ct)
+        => await mediator.Send(new ListContractChangelogsQuery(id), ct);
 }
 
 public record TransitionContractBody(ContractPhase TargetPhase, ApprovalDecision Decision, string? Comment);