billboard applets: drop billboard- prefix from partials & ids; Most Recent → Most Recent Scroll; room_scroll → scroll — TDD

- Slug renames (mig 0004): billboard-my-scrolls → my-scrolls; billboard-my-contacts → my-contacts; billboard-most-recent → most-recent-scroll (name → "Most Recent Scroll"); billboard-notes → notes
- Partial filenames lose the `billboard-` token to mirror dashboard/gameboard convention; element ids follow (id_applet_my_scrolls, id_applet_my_contacts, id_applet_most_recent_scroll, id_applet_notes, id_applet_scroll); .applet-billboard-scroll → .applet-scroll
- View fn billboard.views.room_scroll → scroll; template apps/billboard/room_scroll.html → scroll.html (URL name `billboard:scroll` already correct)
- ITs + FTs updated to new identifiers; SCSS selectors retitled

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Sonnet 4.6 <noreply@anthropic.com>

src/apps/billboard/urls.py

@@ -11,6 +11,6 @@ urlpatterns = [
     path("note/<slug:slug>/set-palette", views.note_set_palette, name="note_set_palette"),
     path("note/<slug:slug>/don", views.don_title, name="don_title"),
     path("note/<slug:slug>/doff", views.doff_title, name="doff_title"),
-    path("room/<uuid:room_id>/scroll/", views.room_scroll, name="scroll"),
+    path("room/<uuid:room_id>/scroll/", views.scroll, name="scroll"),
     path("room/<uuid:room_id>/scroll-position/", views.save_scroll_position, name="save_scroll_position"),
 ]