Make the HMR WebSocket URL follow the page URL

[addshore]

Configure devServer.client.webSocketURL as the special auto://0.0.0.0:0/ws URL to make the HMR client derive the protocol, hostname, and port from the page loaded by the browser.

This makes host-browser development connect to ws://localhost:8081/ws, while containerized browser tests (e.g. Selenium) continue to reach http://ui:8081.

Similar to #1207, this fixes the local HMR issue, but without causing CI to fail.

Validated locally:

• Vue unit tests pass.
• Host browser opened the webpack HMR WebSocket at ws://localhost:8081/ws.
• Docker Compose health check and a Selenium container both received HTTP 200 from http://ui:8081.
• End-to-end browser tests pass in a CI-like Docker Compose setup

[github-actions]

Deployment previews on netlify for branch refs/pull/1218/merge will be at the following locations (when build is done):

• UI with mock store: https://a69a61f2f8-mock--wbstack-ui.netlify.app/
• UI pointing to prod: https://a69a61f2f8-prod--wbstack-ui.netlify.app/

[outdooracorn]

Thanks for looking into this and submitting a PR! This works for me locally.

One clarification: this setting controls the WebSocket URL used by the browser's HMR client; it does not bind the Vue dev server to 0.0.0.0. The server's bind address is controlled by --host / devServer.host, and remains set by --host ui in docker-compose.yml.

I've added a comment to the devServer.client.webSocketURL setting and updated the PR title and description to reflect this.