Script pane, realtime peer sync, and logout button

- Script pane: PDF tab beside annotations; "Add script annotation" arms
  highlight mode on the draft, ✓/✕ to confirm/cancel, auto-scrolls to the
  active annotation's highlights during playback. Adds Project.script.
- Realtime: Django Channels websocket per project broadcasts attributed
  scene deltas after each save; peers merge them in (keeping local drafts).
- Logout link in the editor project-bar.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scenes/routing.py

@@ -0,0 +1,7 @@
+from django.urls import path
+
+from .consumers import SceneConsumer
+
+websocket_urlpatterns = [
+    path('ws/projects/<int:pk>/', SceneConsumer.as_asgi()),
+]