Add the dualpath-as-single-machine site toggle

Most facilities consider a Dualpath pair one physical dual-bay machine.
New site setting dualpath_single_machine (default on): the machines
list, dashboard counts, machines-by-type report, and floor map collapse
each pair to its primary bay (lower assetnumber), with combined
2007 / 2008 labels; pagination totals stay honest. Detail pages remain
per-bay and always show a dual-bay sibling banner linking the partner.
Pair resolution lives in core services and joins the plugin contract
surface (0.8.0 -> 0.9.0).

On the WJ dataset: 31 pairs collapse, machine counts 262 -> 231, map
470 assets. Toggle verified live in both states, left on.

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

shopdb/api/__init__.py

@@ -65,6 +65,12 @@ from shopdb.utils.import_mode import (
     parse_import_datetime,
 )
 
+# Dualpath single-machine collapse (a dual-bay pair is one physical machine)
+from shopdb.core.services.dualpath import (
+    resolve_dualpath_pairs,
+    dualpath_single_machine_enabled,
+)
+
 # Legacy employee directory lookup (read-only) used by notifications
 from shopdb.utils.employee_db import employee_connection
 
@@ -214,6 +220,8 @@ __all__ = [
     # Helpers
     'audit_log',
     'resolve_asset_position',
+    'resolve_dualpath_pairs',
+    'dualpath_single_machine_enabled',
     # Infrastructure
     'db',
     'cache',