feat: add option to disable pixel placement

polylan_submitter/place/signals.py

@@ -1,11 +1,12 @@
-"""Reacts to an admin editing a PlaceSettings row (grid size) by:
+"""Reacts to an admin editing a PlaceSettings row (grid size, placement
+toggle) by:
 
 1. Rebuilding that event's Redis canvas from history at the (possibly new)
    dimensions - a resize invalidates the old Redis bytes (wrong length,
    wrong meaning), so this keeps Redis self-healing instead of relying on
    the admin remembering to click "Resync canvas from DB" after every
    resize.
-2. Pushing the new size to that event's already-connected clients. Unlike
+2. Pushing the new settings to that event's already-connected clients. Unlike
    the clock app, place has no periodic heartbeat broadcast to piggyback
    this onto, so it's broadcast explicitly here instead.
 """
@@ -33,5 +34,6 @@ def on_settings_saved(sender, instance, **kwargs):
             "type": "settings_changed",
             "width": instance.width,
             "height": instance.height,
+            "placement_enabled": instance.placement_enabled,
         },
     )