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/coredata/migrations/20260608T122627Z.sql

@@ -0,0 +1,70 @@
+-- Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+CREATE TABLE risk_assessment_boundaries (
+    id TEXT PRIMARY KEY,
+    tenant_id TEXT NOT NULL,
+    organization_id TEXT NOT NULL,
+    risk_assessment_scope_id TEXT NOT NULL REFERENCES risk_assessment_scopes(id) ON DELETE CASCADE,
+    parent_boundary_id TEXT REFERENCES risk_assessment_boundaries(id) ON DELETE SET NULL,
+    name TEXT NOT NULL,
+    created_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    updated_at TIMESTAMP WITH TIME ZONE NOT NULL,
+    CONSTRAINT risk_assessment_boundaries_unique_name UNIQUE (risk_assessment_scope_id, name)
+);
+
+ALTER TABLE risk_assessment_nodes
+    ADD COLUMN boundary_id TEXT REFERENCES risk_assessment_boundaries(id) ON DELETE SET NULL;
+
+-- Migrate legacy BOUNDARY-typed nodes into the first-class boundary model.
+-- Each boundary gets a freshly generated GID (entity type 101). Node names are
+-- already unique per scope, so the boundary (scope_id, name) constraint cannot
+-- be violated.
+INSERT INTO risk_assessment_boundaries (
+    id,
+    tenant_id,
+    organization_id,
+    risk_assessment_scope_id,
+    parent_boundary_id,
+    name,
+    created_at,
+    updated_at
+)
+SELECT
+    generate_gid(decode_base64_unpadded(tenant_id), 101),
+    tenant_id,
+    organization_id,
+    risk_assessment_scope_id,
+    NULL,
+    name,
+    created_at,
+    updated_at
+FROM risk_assessment_nodes
+WHERE node_type = 'BOUNDARY';
+
+-- Remove the legacy node representation now that the boundaries exist.
+DELETE FROM risk_assessment_nodes
+WHERE node_type = 'BOUNDARY';
+
+-- Drop the now-unused BOUNDARY value from the node_type enum. PostgreSQL cannot
+-- remove a value from an enum in place, so the type is rebuilt without it.
+ALTER TYPE risk_assessment_node_type RENAME TO risk_assessment_node_type_old;
+
+CREATE TYPE risk_assessment_node_type AS ENUM ('ENTITY', 'ASSET', 'DATA');
+
+ALTER TABLE risk_assessment_nodes
+    ALTER COLUMN node_type TYPE risk_assessment_node_type
+    USING node_type::text::risk_assessment_node_type;
+
+DROP TYPE risk_assessment_node_type_old;