Stack upgrade skips transitional states (installing, starting) over MQTT

### Current Behavior

**Related:** #7324, PR #7573

When upgrading a running instance's Node-RED version, the state changes reported over MQTT are:

`running → stopped → running`

Looks like the inflight state during a stack upgrade jumps straight to `starting` without going through `installing` first (there's even a `// TODO: better inflight state needed` comment in the upgrade path in `forge/routes/api/project.js`). The intermediate states might just need to be set and published at the right points in the upgrade flow.

### Expected Behavior

`running → stopped → installing → starting → running`

The `installing` and `starting` transitional states are never emitted.

### Steps To Reproduce

1. Have a hosted instance in `running` state
2. Update its Node-RED version (stack)
3. Watch the state changes over MQTT — `installing` and `starting` are skipped

### Environment

- FlowFuse version: 2.32.0
- Node.js version:
- npm version:
- Platform/OS:
- Browser:

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

I have provided an initial effort estimate