[BUG] Socketio path is not dynamically adjusting correctly in edge cases (with fix proposal)

this issue is related to this: https://github.com/frappe/frappe_docker/issues/1481 https://github.com/frappe/frappe_docker/issues/1783 https://github.com/frappe/frappe/issues/33159 https://github.com/frappe/frappe/issues/32436 https://github.com/frappe/frappe/issues/32436#issue-3043489310

Context:

1. i am setting my own networking for frappe site,
2. i set somekind of reverse proxy server in front of my frappe server.
3. in edge cases like me the socketio fails to dynamically adjust.

To reproduce:

1. first i bench new-site oldsite.com
2. same basic setup bench install-app etc and so on...
3. app is up and running, able to login but websockets failed to connect and fallback to polling.

after some debugging i got it working. so here i am just reporting it

refering to this code: https://github.com/frappe/frappe/blob/35c1cc0276f5849325a9370327a31762f920eb51/frappe/public/js/frappe/socketio_client.js#L116C1-L127C3

in my case this specific function returns subdomain.mysite.com:9000/sitename.com/socket.io/ when i was expecting subdomain.mysite.com/socket.io/

so 2 problem:

1. there shouldn't be any port showing up
2. path shouldn't contain sitename

below is the way i adjust it to work i need it to return host instead of host/sitename.com which is some random site i chose when creating bench new-site

i understand that the existing code is tring to cater the needs of multitenancy, but i think instead of assuming right away that the site is mutitenant with /sitename.com as path, perhaps there might be ways to dynamically autoadjust it or configure it maybe in common_site_config or smth? eg : socketio_path :"/" or "/{}"

in my case i did it like so:

get_host(port = 9000) {
    let host = window.location.origin;
    // somehow changing developer_mode 1 doesnt cause this windows.dev_server to change to false
    // causing the site to return <sitename>:<port>

    // dev_server originally indicates development vs production build mode, 
    // but netwo