dashboarddefaults: pick a kiosk from a dropdown (auto-fill FQDN) + Location wording

Adds GET /api/computers/display-kiosks - the displays that reported in (Kiosk
type), each with its derived FQDN (F<serial>.<domain>). The Dashboard Defaults
form gets a kiosk dropdown that fills the FQDN so admins pick a display instead
of typing an IP; IP stays an optional manual field. Table shows FQDN or IP.
'Business Unit' label -> 'Location' on this page + the settings nav.

tests/test_core/test_display_kiosks.py

@@ -0,0 +1,45 @@
+"""The /computers/display-kiosks picker: reporting displays with a derived FQDN.
+
+Feeds the Dashboard Defaults kiosk dropdown so an admin picks a display instead
+of typing an IP. The FQDN is F<serial>.<domain> (device naming), derived from the
+BIOS serial the collector already reports.
+"""
+import pytest
+
+from shopdb.core.models import AssetType
+from plugins.computers.models import ComputerType
+
+KEY = 'testcollectorkey'
+
+
+@pytest.fixture
+def collector_key(app):
+    old = app.config.get('COLLECTOR_API_KEY')
+    app.config['COLLECTOR_API_KEY'] = KEY
+    yield KEY
+    app.config['COLLECTOR_API_KEY'] = old
+
+
+def test_display_kiosks_derives_fqdn(client, db, collector_key):
+    db.session.add(AssetType(assettype='computer', pluginname='computers',
+                             tablename='computers'))
+    db.session.add(ComputerType(computertype='Kiosk'))
+    db.session.commit()
+
+    # a display reports in via the collector (pctype -> Kiosk type, with serial)
+    resp = client.post('/api/collector/computers', json={
+        'hostname': 'WJDISP01', 'serialnumber': 'ABC1234',
+        'pctype': 'gea-shopfloor-display',
+    }, headers={'X-API-Key': KEY})
+    assert resp.status_code == 200, resp.data
+
+    rows = client.get('/api/computers/display-kiosks').get_json()['data']
+    match = [k for k in rows if k['hostname'] == 'WJDISP01']
+    assert match, rows
+    assert match[0]['fqdn'] == 'fabc1234.device.geaerospace.net'
+    assert match[0]['serialnumber'] == 'ABC1234'
+
+
+def test_display_kiosks_empty_when_no_kiosk_type(client, db):
+    # No 'Kiosk' ComputerType -> empty list, not an error.
+    assert client.get('/api/computers/display-kiosks').get_json()['data'] == []