Move relationship types + dashboard recent off the machines blueprint

- Add /api/assets/relationshiptypes (GET/POST) serving RelationshipType; point
  relationshipTypesApi at it instead of the legacy /api/machines blueprint.
- Dashboard recent-devices widget reads assetsApi.list (asset shape) instead
  of machinesApi.

No frontend code references machinesApi anymore.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

shopdb/core/api/assets.py

@@ -203,6 +203,51 @@ def delete_asset_status(status_id: int):
     return success_response(message='Asset status deleted')
 
 
+# =============================================================================
+# Relationship Types
+# =============================================================================
+
+@assets_bp.route('/relationshiptypes', methods=['GET'])
+@jwt_required(optional=True)
+def list_relationship_types():
+    """List all asset relationship types."""
+    types = RelationshipType.query.order_by(RelationshipType.relationshiptype).all()
+    return success_response([{
+        'relationshiptypeid': t.relationshiptypeid,
+        'relationshiptype': t.relationshiptype,
+        'description': t.description
+    } for t in types])
+
+
+@assets_bp.route('/relationshiptypes', methods=['POST'])
+@jwt_required()
+def create_relationship_type():
+    """Create a new asset relationship type."""
+    data = request.get_json()
+    if not data or not data.get('relationshiptype'):
+        return error_response(ErrorCodes.VALIDATION_ERROR, 'relationshiptype is required')
+
+    if RelationshipType.query.filter_by(relationshiptype=data['relationshiptype']).first():
+        return error_response(
+            ErrorCodes.CONFLICT,
+            f"Relationship type '{data['relationshiptype']}' already exists",
+            http_code=409
+        )
+
+    rel_type = RelationshipType(
+        relationshiptype=data['relationshiptype'],
+        description=data.get('description')
+    )
+    db.session.add(rel_type)
+    db.session.commit()
+
+    return success_response({
+        'relationshiptypeid': rel_type.relationshiptypeid,
+        'relationshiptype': rel_type.relationshiptype,
+        'description': rel_type.description
+    }, message='Relationship type created', http_code=201)
+
+
 # =============================================================================
 # Assets
 # =============================================================================