Set outbound wires for a node

## Context

Parent: #6897 — FE MQTT Migration

Migrate the `custom:set-wires` action from HTTP to MQTT transport. This action allows the Expert to programmatically set outbound wires for a node, connecting nodes together.

## Scope

- Implement `custom:set-wires` over MQTT
- Need to check for removal and editing of existing wires (not just adding new ones)

## Estimate

1h

## Acceptance Criteria

- [ ] Expert can set outbound wires for a node via MQTT message
- [ ] Existing wires can be removed or edited, not just added
- [ ] Wire routing renders correctly in the editor