Basic auth prompts multiple times on first access in standalone Docker image

[devi4nt]

Summary

Running the standalone Docker image (ghcr.io/pontusab/workbench-standalone)
with AUTH_USERNAME / AUTH_PASSWORD set, the browser's HTTP basic-auth
dialog appears multiple times on first access to the dashboard. You must
enter the same credentials repeatedly before the dashboard is usable.

This is consistent and reproducible across multiple browsers, separate
machines, and different networks/locations, so it isn't a local cache quirk.

Environment

• Image: ghcr.io/pontusab/workbench-standalone:0.9.1
  (@sha256:5c9122d519ca1333914b42d2a697165f49c001dff020c38f873d22de4728dae0)
• Deployment: standalone container behind a public HTTPS domain (Railway)
• Auth: AUTH_USERNAME / AUTH_PASSWORD set; READONLY=false
• Reproduced on: Chrome, Safari, Firefox; macOS and Windows; multiple networks

Steps to reproduce

1. Deploy the standalone image with AUTH_USERNAME / AUTH_PASSWORD set.
2. Open the public dashboard URL in a fresh browser session for the first time.
3. Enter the credentials when prompted.
4. Observe: the basic-auth dialog reappears one or more times before the
   dashboard finishes loading.

Expected

A single basic-auth prompt on first access - the browser should cache and
replay the credential to all subsequent same-origin requests.