Unified endpoint config type: one Host/IP : Port control in admin

New configSchema type 'endpoint' declared in the module spec: anything
that points at a device or service on the network must be one endpoint
field, rendered identically for every module in /admin as a joined
Host/IP : Port control and stored/handed to the module server as
{ host, port }. Migrates all three connection modules — ProdCom (was a
full URL field), ProPresenter and Timers (were separate host + port
fields). Legacy stored configs (prodcomUrl / flat host+port) keep
working until the admin form is re-saved, at which point the new shape
replaces them. MODULE-GUIDE documents the type and the presentation
rule: no split host/port fields, and full URLs only for genuine web
addresses.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RNYUv9EyrGSFmCnmH7WYKH

public/admin/admin.css

@@ -93,6 +93,12 @@ body { overflow: auto; }
 
 .module-form { margin-top: 12px; border-top: 1px solid var(--border); padding-top: 12px; }
 .module-form .field { max-width: 420px; }
+
+/* endpoint fields: every module's upstream is entered the same way */
+.field .endpoint-row { display: flex; align-items: center; gap: 7px; }
+.endpoint-row .ep-host { flex: 1; min-width: 0; }
+.endpoint-row .ep-port { width: 92px; flex: none; }
+.endpoint-row .ep-sep { color: var(--muted); font-weight: 600; }
 .module-form-empty { color: var(--muted); font-size: 12px; margin-top: 10px; }
 
 .module-actions {