FF Expert settings management across multiple instances (FlowFuse platform)

**Parent Deliverable:** FlowFuse/product#47 — Expert as Agentic Co-pilot

### Description

Enable FF Expert to view, audit, and adjust Node-RED and FlowFuse settings across multiple instances when used from the FlowFuse platform interface (outside the immersive editor).

### User Story

As a FlowFuse platform user managing multiple Node-RED instances, I want FF Expert to help me audit and standardize settings across my fleet so that I can ensure consistency and identify configuration drift.

### Capabilities

**Audit:**
- Compare settings across multiple instances
- Identify inconsistencies or drift from standards
- Flag security or configuration concerns across the fleet
- Generate reports on settings compliance

**Adjust:**
- Apply settings changes to multiple instances
- Standardize configuration across a team or application
- Roll out FlowFuse-recommended settings at scale

### Scope Considerations

This is a broader scope than single-instance management. Before implementation, we need to review and decide:

- [ ] Which settings should be adjustable at platform level vs instance level?
- [ ] What's the right UX for bulk operations (preview, confirmation, rollback)?
- [ ] How do we handle instances that are offline or in different states?
- [ ] What FlowFuse settings (not just Node-RED) should Expert manage?
- [ ] Should this integrate with Instance Types / Templates for standardization?

### Prerequisites

- FlowFuse/flowfuse#6497 (communication between FF Expert and NR Assistant)
- Single-instance settings management (FlowFuse/flowfuse#6504)

### Epic/Story

_No response_

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate