Add risk assessment boundary model

Introduce RiskAssessmentBoundary as a first-class, self-nesting entity that
groups nodes within a risk assessment scope, and thread it through every
surface.

- coredata: new risk_assessment_boundaries table + migration, boundary_id on
  nodes, self-referential parent_boundary_id, entity type registration
- riskmanagement: boundary CRUD service methods, boundary_id wiring on node
  create/update, scope-membership and self-parent validation, nested-subgraph
  Mermaid rendering
- IAM: core:risk-assessment-boundary:{get,list,create,update,delete} actions
  and viewer/auditor read policies
- console GraphQL: RiskAssessmentBoundary type, connection, order enum, CRUD
  mutations, boundaries field on scope, boundaryId on nodes
- CLI: risk-assessment boundary command group and --boundary-id on nodes
- MCP: boundary tools and boundary_id on node tools
- n8n: boundary operations and boundary fields on node operations
- console UI: boundary list/create/edit, boundary selector on nodes, diagram
  refetch on boundary changes

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/server/api/console/v1/base_resolvers.go

@@ -170,6 +170,16 @@ func (r *queryResolver) Node(ctx context.Context, id gid.GID) (types.Node, error
 
 			return types.NewRiskAssessmentScope(s), nil
 		}
+	case coredata.RiskAssessmentBoundaryEntityType:
+		action = probo.ActionRiskAssessmentBoundaryGet
+		loadNode = func(ctx context.Context, scope *coredata.Scope, id gid.GID) (types.Node, error) {
+			b, err := r.riskManagement.GetBoundary(ctx, scope, id)
+			if err != nil {
+				return nil, err
+			}
+
+			return types.NewRiskAssessmentBoundary(b), nil
+		}
 	case coredata.RiskAssessmentScenarioEntityType:
 		action = probo.ActionRiskAssessmentScenarioGet
 		loadNode = func(ctx context.Context, scope *coredata.Scope, id gid.GID) (types.Node, error) {