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/__init__.py

@@ -23,7 +23,11 @@ from .plugins import plugin_manager
 # 0.7.0: added the four ADR-010 frontend-contribution hooks (get_settings_cards,
 # get_asset_panels, get_map_overlays, get_asset_presentation), consumed by the
 # GET /api/pluginui/* endpoints. Four additive optional hooks, one minor bump.
-__contract_version__ = '0.8.0'
+# 0.9.0: added the dualpath single-machine collapse helpers to shopdb.api
+# (resolve_dualpath_pairs, dualpath_single_machine_enabled), consumed by the
+# machines plugin list/detail to collapse dual-bay pairs. Two additive names,
+# minor bump.
+__contract_version__ = '0.9.0'
 
 # Product release version (see ADR-007). The product version and the
 # plugin-contract version above are distinct series with independent