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/models.py

@@ -16,6 +16,7 @@ class Project(models.Model):
     name = models.CharField(max_length=200)
     otio = models.FileField(upload_to="otio/", blank=True, null=True)
     clip = models.FileField(upload_to="clips/", blank=True, null=True)
+    script = models.FileField(upload_to="scripts/", blank=True, null=True)
     fps = models.FloatField(default=NTSC_24)
     thumbnail_status = models.CharField(max_length=20, default="missing")
     thumbnail_manifest = models.JSONField(default=dict, blank=True)