fix(dashboardAPI): show string fields in stat panels (reduceOptions.fields)

Grafana Stat/Gauge panels default the Fields option to "Numeric Fields"
(reduceOptions.fields == ""), so string-valued fields (mode, state,
movementState, direction, flowSource, predictionQuality, running) are excluded
and the panel renders "No data" even though the Flux query (last()) returns the
string correctly.

Set reduceOptions.fields = "/.*/" ("All fields") on every stat panel bound to a
string field across machine, machineGroup, pumpingStation, valve,
valveGroupControl, and monster templates. lastNotNull calc was already correct.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

config/valveGroupControl.json

@@ -22,6 +22,7 @@
       "datasource": { "type": "influxdb", "uid": "cdzg44tv250jkd" },
       "gridPos": { "h": 5, "w": 8, "x": 0, "y": 1 },
       "id": 2,
+      "options": { "reduceOptions": { "calcs": ["lastNotNull"], "fields": "/.*/" }, "colorMode": "value", "graphMode": "none" },
       "targets": [
         {
           "query": "from(bucket: \"${bucket}\")\n  |> range(start: -30d)\n  |> filter(fn:(r) => r._measurement==\"${measurement}\" and (r._field==\"mode\" or r._field==\"maxDeltaP\"))\n  |> last()",