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/machineGroup.json

@@ -61,7 +61,8 @@
         "reduceOptions": {
           "calcs": [
             "lastNotNull"
-          ]
+          ],
+          "fields": "/.*/"
         },
         "colorMode": "value",
         "graphMode": "none"
@@ -521,4 +522,4 @@
   "title": "template",
   "uid": null,
   "version": 1
-}
+}