pco-plan: everything configured in Admin; key, section and top-bar restyle

- Drops the separate setup page: the service type is a select grouped by
  Planning Center folder path (GET /service-types), the pinned plan a
  select of upcoming/recent plans that follows the chosen service type
  (GET /plans?serviceTypeId=), credentials sit in a group that folds once
  saved.
- Show/hide moves from per-tile settings to a server-wide checklist in
  Admin (three columns, folded by default): top bar, series, part, service
  type, date, service time, total length, running clock, countdown,
  headers, item numbers, start times, length, type badge, key, arrangement,
  author/CCLI, description, notes, pre/post-service items, now indicator,
  item runtime, dim completed, ProPresenter line. Tiles keep only text
  size and auto-scroll.
- Top bar text is a template with placeholders ({series} • {part} |
  {serviceType} • {date} by default; • separates droppable segments, |
  starts the second line).
- Song key: larger, admin-chosen color (blue by default), always right
  after the title and before the type badge. Section headers are
  full-width accent bands. Optional background tint per item type.
- tools/pco-mock.js plan titles are part numbers, as in a real series.

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

README.md

@@ -137,13 +137,15 @@ ignored from then on.
   ProPresenter endpoint (host : port), password.
 - **PCO Plan** — the order of service from Planning Center Services: every
   plan item with its scheduled start time, length, type, song key,
-  description and item notes (each detail is a per-tile show/hide setting).
-  When the ProPresenter module is running it follows that module's live
-  item, highlights the matching plan item, dims what's done and shows the
-  elapsed vs planned runtime and how far ahead/behind the service is. Admin
-  config: Planning Center credentials (Personal Access Token app ID + secret,
-  or an OAuth token) and the service type — browse your Planning Center
-  folders and pick it at `/modules/pco-plan/setup.html`.
+  description and item notes. When the ProPresenter module is running it
+  follows that module's live item, highlights the matching plan item, dims
+  what's done and shows the elapsed vs planned runtime and how far
+  ahead/behind the service is. Everything is configured in `/admin`:
+  Planning Center credentials (Personal Access Token app ID + secret, or an
+  OAuth token), the service type (a list grouped by your Planning Center
+  folders), an optional pinned plan, the top-bar text (placeholders such as
+  `{series} • {part} | {serviceType} • {date}`), colors, and a show/hide
+  checklist for every detail. Tiles only choose their text size.
 - **Clock** — a big booth clock; also the smallest possible module and the
   reference for module authors.