Move self-deletion guard from handler into AdminService (DeleteUser) to fix SoC violation

- Add ErrCannotDeleteSelf sentinel error in service layer.
- Change DeleteUser signature to (ctx, callerID, id) across all layers.
- Move self-deletion guard from handleDeleteUser handler into userAdminService.DeleteUser.
- Update handleError to map ErrCannotDeleteSelf to 400 BadRequest.
- Adjust all affected tests to use the new signature.

1 files changed, 4 insertions, 4 deletions

diff --git a/internal/api/handlers_admin.go b/internal/api/handlers_admin.go
index 6d10c67..d68b07c 100644
--- a/internal/api/handlers_admin.go
+++ b/internal/api/handlers_admin.go
@@ -83,11 +83,11 @@ func (s *Server) handleDeleteUser(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	adminUser, _ := r.Context().Value(userCtxKey).(*model.User)
-	if adminUser != nil && adminUser.ID == id {
-		badRequest(w, "cannot delete self")
-		return
+	var callerID int64
+	if adminUser != nil {
+		callerID = adminUser.ID
 	}
-	if err := s.adminSvc.DeleteUser(r.Context(), id); err != nil {
+	if err := s.adminSvc.DeleteUser(r.Context(), callerID, id); err != nil {
 		handleError(w, err)
 		return
 	}