Fix proxy HTTPS address comparison missing replace argument (#4511)

`address.replace('http')` without a second argument replaces "http"
with the string "undefined" in JavaScript, causing `isCurrentAddress()`
to always return false when using an HTTPS reverse proxy in front of
Plan's HTTP server.

This breaks subpath routing — the React app falls back to an empty
`baseAddress`, so the router has no basename and API calls go to
relative paths instead of the configured address.

Adding the missing empty string argument (`address.replace('http', '')`)
correctly strips the protocol for comparison.

Author: Leolebleis

Plan/react/dashboard/src/service/backendConfiguration.js

@@ -10,7 +10,7 @@ const isCurrentAddress = (address) => {
     let is = window.location.href.startsWith(address);
     const usingProxyHttps = window.location.href.startsWith("https") && !address.startsWith("https");
     if (usingProxyHttps) {
-        is = window.location.href.replace('https', '').startsWith(address.replace('http'));
+        is = window.location.href.replace('https', '').startsWith(address.replace('http', ''));
     }
     if (!is) {
         console.warn(`Configured address ${address} did not match start of ${window.location.href}, falling back to relative address. Configure 'Webserver.Alternative_IP' settings to point to your address.`)