ADR-013 Phase 3: generic map-overlays renderer (Path A)

Wires the ADR-010 get_map_overlays hook into the floor map so a plugin decorates
markers as JSON, no map code. ShopFloorMap fetches /api/pluginui/map-overlays,
then each overlay's endpoint (per-asset [{assetid, color, label}]), joins by
assetid, and draws a ring or badge circleMarker on matching markers plus a
legend entry - all as extra Leaflet layers cleared and redrawn with the markers.

Aligned the measuringtools calibration overlay endpoint to the documented
contract: it now returns {assetid, color, label} (was {calibrationstatus,
statuscolor}) and only decorates due/overdue tools.

Additive + guarded (assetid null check, per-endpoint try/catch, cleanup on
re-render), so the map degrades to no decorations on any failure. Verified: the
overlay endpoint serves the contract shape, the map renders without error, and
the frontend builds. A populated badge needs a site that actually places
measuring tools on its map (this dataset places none). 38 measuringtools/pluginui
tests, 58 vitest, build + naming green.

plugins/measuringtools/api/routes.py

@@ -363,13 +363,18 @@ def map_overlay():
     """
     today = date.today()
     query = db.session.query(MeasuringTool).join(Asset).filter(Asset.isactive == True)
+    # Overlay contract (ADR-010): [{assetid, color, label}] joined by assetid.
+    # Only decorate tools that are actually due/overdue - a marker with no entry
+    # gets no badge.
     data = []
     for tool in query.all():
         status = derive_status(tool.nextcalibrationdate, today)
+        if status not in ('overdue', 'duesoon'):
+            continue
         data.append({
             'assetid': tool.assetid,
-            'calibrationstatus': status,
-            'statuscolor': STATUS_COLORS.get(status, STATUS_COLORS['unknown']),
+            'color': STATUS_COLORS.get(status, STATUS_COLORS['unknown']),
+            'label': 'Overdue' if status == 'overdue' else 'Due soon',
         })
     return success_response(data)