skip the selection-edge query where nothing reads it

The temporal timeline summarises every snapshot in a series. Each summary now
also counts how many features the selection edge cuts, but a timeline point
renders values only, so that was one database round trip per snapshot for a
disclosure nobody sees. Make it opt-out and have the timeline opt out.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/tests/test_sprint187_temporal_map_foundation.py

@@ -320,7 +320,7 @@ def test_temporal_compare_returns_delta_and_canonical_change_payload(monkeypatch
     def get_dataset(_db, _project_id, dataset_id, _label):
         return earlier if dataset_id == earlier.id else later
 
-    def summarize(_db, *, dataset, bbox):  # noqa: ARG001
+    def summarize(_db, *, dataset, bbox, disclose_selection_edge=True):  # noqa: ARG001
         value = 100.0 if dataset.id == earlier.id else 115.0
         return {
             "metric_label": "Inwoners",
@@ -386,7 +386,7 @@ def test_temporal_comparison_clips_cross_boundary_bbox_to_selected_area(monkeypa
         staticmethod(lambda _db, _project_id, requested_area_id: area if requested_area_id == area_id else None),
     )
 
-    def summarize(_db, *, dataset, bbox, selection_geometry, full_dataset_area):  # noqa: ARG001
+    def summarize(_db, *, dataset, bbox, selection_geometry, full_dataset_area, disclose_selection_edge=True):  # noqa: ARG001
         captured_geometries.append(selection_geometry)
         return {
             "metric_label": "Oppervlakte",