Deleting the old UI took its connection panel with it, so the plugin installed,
opened, and had nowhere to type a URL. The frame would have loaded and answered
503 on every request inside it — which reads as Gitea being down rather than as
nobody having said where Gitea is.
The panel now asks for the connection FIRST and shows the form when there is
none.
Two halves, and which one you get depends on who you are: the URL is the
owner's, one instance per server, and everyone else supplies only a token and
inherits it. Not a UI choice — service_connections stores a member's row with a
null URL for exactly this reason, so "members never see the instance URL" is a
property of the schema rather than a filter somebody has to remember.
Defaults to http://localhost:3000 and says why in the field: the sidecar
fetches SERVER-side, so localhost means the machine Officer runs on. It needs
no TLS and never leaves the box, where the public URL takes the same traffic
out and back.