The "Layout Editor" Save button for Dashboard Pages (when clicked) redirects to the wrong URL if altered RED.settings.httpNodeRoot

### Current Behavior

Related to issue #1927
Button "Layout Editor" works fine, but the Save button has similar issue and does not work if RED.settings.httpNodeRoot is other than default (e.g. "node-red"): There is a 2nd /node-red in the built URL

Example (settings.json): httpNodeRoot = "node-red"

https://..../**node-red/node-red**/dashboard/api/v1/eb98e9e4f268f7cc/flows 404 (Not Found)

### Expected Behavior

### Steps To Reproduce

Node-RED settings.json: httpNodeRoot = "node-red"
Start Node-RED
Create any Dashboard with a single element
Press Edit Layout button
Change Layout
Press Save Layout
->404

### Environment

- Dashboard version: 1.30.2
- Node-RED version: 4.1.10
- Node.js version: 24.16.0
- npm version: Shipped with 24.16.0
- Platform/OS: Linux
- Browser: Edge

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

I have provided an initial effort estimate