Fix for a blank loading screen when opening the UI over plain HTTP

Fixed a bug where the web interface stayed on a blank “Loading…” screen when reached over plain HTTP. The browser was being told to upgrade every asset request to HTTPS even when the page itself was served over HTTP, so those assets failed to load. Asset requests are now upgraded only when the page itself is served over HTTPS.

No action required. The interface loads correctly whether reached by IP over HTTP or through a TLS ingress.