Scope mapping writes and stabilize sibling lookup

The tracker-mapping worker loaded a pattern in its claim transaction and
committed the resolution in a separate, later transaction. A full-row
Update would write back stale values and clobber any user edit made in
between. Add UpdateMapping, which writes only the worker-resolved
columns (common_tracker_pattern_id, third_party_id, and a description
filled only when still empty), leaving user-editable fields untouched.

Also add ORDER BY tracker_pattern_id to the sibling pattern lookup: the
query used LIMIT without an ORDER BY, so an over-limit match set
returned an arbitrary subset and could resolve the third party
differently across runs.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/cookiebanner/tracker_mapping_worker.go

@@ -267,7 +267,7 @@ func (h *trackerMappingHandler) Process(ctx context.Context, tp coredata.Tracker
 					}
 				}
 
-				if err := tp.Update(ctx, tx, scope); err != nil {
+				if err := tp.UpdateMapping(ctx, tx, scope); err != nil {
 					return fmt.Errorf("cannot update tracker pattern mapping: %w", err)
 				}