No campus's address ships in the repo

prodcom-transcript's endpoint defaulted to 10.3.11.152:24480 — Apollo
Beach's ProdCom. A fresh install anywhere therefore came up reading AB's
comms and reported itself healthy doing it: that is exactly what the new
North Attleboro install did. The default is now blank, so a new install
says "No ProdCom server configured" (in red, as the ProPresenter modules
already do for a missing host) until someone points it at the ProdCom for
that location. Setting a host still connects as before.

The same address is out of SPEC.md's worked example, CLAUDE.md's note
about the reference app, and the prodcom-listener snapshot's config,
README and fallback — that fallback now exits with a line telling the
operator what to set, rather than throwing on an empty URL.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -44,7 +44,7 @@ title-bar controls). The rules that matter most:
 - `prodcom-listener/` — live ProdCom transcript web app. Zero-dependency Node
   `server.js` that serves `public/` and proxies `/prodcom/*` (including the SSE
   transcript stream) to the ProdCom API at `config.json → prodcomUrl`
-  (default `http://10.3.11.152:24480`). Good reference for: SSE handling,
+  (set per site; each campus runs its own). Good reference for: SSE handling,
   reconnect logic, channel colors/filtering, PWA install.
 - `band-lineup-display/` — backstage Electron app (stage lineup photos with
   mic/pack labels) plus ProPresenter Now/Next: