Fix prop renders

* Incorporate prop scaling
* Props now render to a canvas

db/schema/tables/045_scene.sql

@@ -210,6 +210,9 @@ CREATE TABLE scene.loose_props (
     -- Position in scene (PostGIS point, SRID 0)
     position public.virtual_point NOT NULL,
 
+    -- Scale factor (10% - 1000%), inherited from prop definition at drop time
+    scale REAL NOT NULL DEFAULT 1.0 CHECK (scale >= 0.1 AND scale <= 10.0),
+
     -- Who dropped it (NULL = spawned by system/script)
     dropped_by UUID REFERENCES auth.users(id) ON DELETE SET NULL,