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/views.py

@@ -85,11 +85,11 @@ def toggle_billboard_applets(request):
 
 
 @login_required(login_url="/")
-def room_scroll(request, room_id):
+def scroll(request, room_id):
     room = Room.objects.get(id=room_id)
     events = room.events.select_related("actor").all()
     sp = ScrollPosition.objects.filter(user=request.user, room=room).first()
-    return render(request, "apps/billboard/room_scroll.html", {
+    return render(request, "apps/billboard/scroll.html", {
         "room": room,
         "events": events,
         "viewer": request.user,