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/cmd/risk-assessment/risk_assessment.go

@@ -17,6 +17,7 @@ package riskassessment
 import (
 	"github.com/spf13/cobra"
 	"go.probo.inc/probo/pkg/cmd/cmdutil"
+	"go.probo.inc/probo/pkg/cmd/risk-assessment/boundary"
 	"go.probo.inc/probo/pkg/cmd/risk-assessment/create"
 	"go.probo.inc/probo/pkg/cmd/risk-assessment/delete"
 	"go.probo.inc/probo/pkg/cmd/risk-assessment/list"
@@ -42,6 +43,7 @@ func NewCmdRiskAssessment(f *cmdutil.Factory) *cobra.Command {
 	cmd.AddCommand(delete.NewCmdDelete(f))
 	cmd.AddCommand(scope.NewCmdScope(f))
 	cmd.AddCommand(node.NewCmdNode(f))
+	cmd.AddCommand(boundary.NewCmdBoundary(f))
 	cmd.AddCommand(process.NewCmdProcess(f))
 	cmd.AddCommand(threat.NewCmdThreat(f))
 	cmd.AddCommand(scenario.NewCmdScenario(f))