alerts: per-support-team webhook; printedparts routes low-stock to a chosen team

Support teams gain a webhookurl (migration 7d29 + API + settings-page field), so
a team is a notification target. send_webhook(url=) lets a caller override the
site default with a team's webhook. Printedparts gains a 'alert support team'
setting (printedparts_alert_supportteamid) + selector on its settings page;
low-stock alerts post to that team's webhook, falling back to the site
alert_webhook_url. Email leg unchanged. Same pattern extends to other alerting
plugins (printers low-toner next).

tests/test_plugins/test_printedparts_ledger.py

@@ -398,3 +398,27 @@ def test_kiosk_take_records_revision_from_qr(client, app, db, directory_employee
                 .filter_by(printeditemid=iid, transactiontype='take')
                 .order_by(PrintedItemTransaction.transactionid.desc()).first())
         assert last.revision is None
+
+
+def test_lowstock_routes_to_support_team_webhook(client, app, db, directory_employee):
+    """A low-stock crossing posts to the selected support team's webhook URL."""
+    from unittest.mock import patch
+    from shopdb.core.models import SupportTeam, Setting
+    with app.app_context():
+        team = SupportTeam(teamname='3D Print Team',
+                           webhookurl='https://teams.example/3dprint')
+        db.session.add(team)
+        db.session.commit()
+        Setting.set('printedparts_alert_supportteamid', str(team.supportteamid))
+        row = PrintedItem(itemcode='3DP-7100', gagelabtag='WJRP7100',
+                          itemname='Widget', quantityonhand=6, lowstockthreshold=5)
+        db.session.add(row)
+        db.session.commit()
+
+    with patch('shopdb.api.send_webhook') as mock_send:
+        # take 2 -> 6 crosses to 4 (<= threshold 5) -> alert fires
+        resp = client.post('/api/printedparts/kiosk/take', json={
+            'itemcode': 'WJRP7100', 'badge': directory_employee, 'quantity': 2})
+        assert resp.status_code == 200, resp.get_json()
+        assert mock_send.called
+        assert mock_send.call_args.kwargs['url'] == 'https://teams.example/3dprint'