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/functional_tests/test_applet_my_notes.py

@@ -105,7 +105,7 @@ class StargazerNoteFromDashboardTest(FunctionalTest):
             defaults={"name": "Palettes", "grid_cols": 6, "grid_rows": 6, "context": "dashboard"},
         )
         Applet.objects.get_or_create(
-            slug="billboard-notes",
+            slug="notes",
             defaults={"name": "Note", "grid_cols": 4, "grid_rows": 4, "context": "billboard"},
         )
         self.gamer = User.objects.create(email="stargazer@test.io")
@@ -323,7 +323,7 @@ class StargazerNoteFromSkyPageTest(FunctionalTest):
             defaults={"name": "My Sky", "grid_cols": 6, "grid_rows": 6, "context": "dashboard"},
         )
         Applet.objects.get_or_create(
-            slug="billboard-notes",
+            slug="notes",
             defaults={"name": "Note", "grid_cols": 4, "grid_rows": 4, "context": "billboard"},
         )
         self.gamer = User.objects.create(email="stargazer@test.io")
@@ -413,7 +413,7 @@ class NoteEquipTitleTest(FunctionalTest):
         super().setUp()
         self.browser.set_window_size(800, 1200)
         Applet.objects.get_or_create(
-            slug="billboard-notes",
+            slug="notes",
             defaults={"name": "My Notes", "grid_cols": 4, "grid_rows": 4, "context": "billboard"},
         )
         self.gamer = User.objects.create(email="stargazer@test.io")