Merge main (PRs #5, #7, #9, #10) into the PCO Plan branch

Resolves the admin form conflicts in favour of this branch's grouped /
collapsible / dependent-select additions (the base hunks were the timers
lane's, ported verbatim), keeps both sides of the README and module-guide
edits, and adopts main's versioning rules: the shell moves to 1.3.0 for the
new schema features (configGroups / instanceGroups, help, color fields,
grouped and dependent selects) and pco-plan 1.3.0 declares
"proddash": ">=1.3.0".

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

modules/pco-plan/module.json

@@ -1,7 +1,8 @@
 {
   "id": "pco-plan",
   "name": "PCO Plan",
-  "version": "1.2.0",
+  "version": "1.3.0",
+  "proddash": ">=1.3.0",
   "description": "Order of service from Planning Center Services, following ProPresenter live",
   "client": "client.js",
   "server": "server.js",