Band Lineup's docs move to where every other module's live

Two things were out of place. `modules/band-lineup/README.md` was the only
README inside any of the eight modules — the guide's folder shape is manifest,
client, server, assets, and every other module is described in this README's
*Included modules* instead. It was also describing a module that no longer
exists: photos and birthdays "come from Planning Center", guests "pinned per
slot", and a refresh interval the manifest has never had.

The entry here had drifted the same way, calling the Drive folder somewhere
to put "manual photos" and the board something Planning Center fills. It is
the other way round now, and has been since 1.10: the board is shared server
state and the source of truth, the photo library fills it, and Sync is
auto-fill that only touches slots nobody placed by hand. The entry says that,
and picks up the Choir spot and the title-bar columns while it is there.

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

README.md

@@ -365,15 +365,24 @@ below. Nothing is installed without someone clicking.
   as `Label | Message` — add `| #channel` to bind one to a channel — and up
   to eight quick emojis).
   Tile settings: avatars, timestamps, names and channel notices.
-- **Band Lineup** — the backstage stage board: everyone scheduled on the
-  band, vocal and production teams for the upcoming Planning Center plan,
-  placed into their mic slot with photo, name and mic/pack label; birthdays
-  in the service week get confetti. Guests and MCs not on the plan are pinned
-  per slot from the title bar's Edit button. Admin config: Planning Center
-  credentials, service type and plan, the teams to include, the stage slots
-  (one mic/pack label per line, in stage order), default columns, and a
-  Google Drive folder for manual photos. Tile settings: names, mic labels,
-  parallax, and the birthday confetti with its intensity.
+- **Band Lineup** — the backstage stage board: everyone on stage in their mic
+  slot with photo, name and mic/pack label, on one shared board that every
+  screen sees the same way — whoever edits it changes it everywhere, over SSE.
+  A photo library fills it: point the module at a Google Drive folder shared
+  "anyone with the link" (file name → person's name) or at a folder on the
+  ProdDash machine, and photos added or removed there follow. **Edit** in the
+  title bar opens that library — drag a photo onto a slot, drag between slots
+  to swap, rename or clear. Planning Center is optional auto-fill on top, not
+  the source of truth: **Sync** reads the upcoming plan's team members and
+  drops each into the slot matching their position, filling only slots nobody
+  placed by hand, so a guest pinned on Thursday survives Sunday's sync.
+  Birthdays in the service week (Wednesday→Tuesday) bring a gold glow and
+  raining confetti, and a Choir button adds the extra spot for the weeks there
+  is one. Admin config: Planning Center credentials, service type and plan, the
+  teams to include, the stage slots (one mic/pack label per line, in stage
+  order), default columns, and the photo folder. Tile settings: parallax,
+  names, mic labels, and birthday confetti with its intensity and a test
+  picker — columns are − / + in the title bar.
 - **Clock** — a big booth clock; also the smallest possible module and the
   reference for module authors.