feat(dashboard): add tank gauge for basin level + 270° arc for fill %

Basin Status group on the Control page now has two visual gauges:

1. gauge-tank (vertical tank with fill gradient) for basin level 0–3 m.
   Color zones: red < 0.6 m (below stopLevel) → orange → blue 1.2–2.5 m
   (normal operating range) → orange → red > 2.8 m (overflow zone).

2. gauge-34 (270° arc) for fill percentage 0–100%.
   Color zones: red < 10% → orange → green 30–80% → orange → red > 95%.

Both gauges are fed from the PS dispatcher's numeric outputs (fillPctNum
and levelNum) which also feed the basin trend charts — same data, two
visual forms.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/pumpingstation-3pumps-dashboard/flow.json

@@ -1889,11 +1889,13 @@
       ],
       [
         "trend_short_basin",
-        "trend_long_basin"
+        "trend_long_basin",
+        "gauge_ps_fill"
       ],
       [
         "trend_short_basin",
-        "trend_long_basin"
+        "trend_long_basin",
+        "gauge_ps_level"
       ],
       [
         "trend_short_basin",
@@ -1901,6 +1903,100 @@
       ]
     ]
   },
+  {
+    "id": "gauge_ps_level",
+    "type": "ui-gauge",
+    "z": "tab_ui",
+    "group": "ui_grp_ps",
+    "name": "Basin level gauge",
+    "gtype": "gauge-tank",
+    "gstyle": "Rounded",
+    "title": "Basin Level",
+    "units": "m",
+    "prefix": "",
+    "suffix": " m",
+    "min": 0,
+    "max": 3,
+    "segments": [
+      {
+        "color": "#f44336",
+        "from": 0
+      },
+      {
+        "color": "#ff9800",
+        "from": 0.6
+      },
+      {
+        "color": "#2196f3",
+        "from": 1.2
+      },
+      {
+        "color": "#ff9800",
+        "from": 2.5
+      },
+      {
+        "color": "#f44336",
+        "from": 2.8
+      }
+    ],
+    "width": 3,
+    "height": 5,
+    "order": 1,
+    "icon": "",
+    "sizeGauge": 20,
+    "sizeGap": 2,
+    "sizeSegments": 10,
+    "x": 900,
+    "y": 760,
+    "wires": []
+  },
+  {
+    "id": "gauge_ps_fill",
+    "type": "ui-gauge",
+    "z": "tab_ui",
+    "group": "ui_grp_ps",
+    "name": "Basin fill gauge",
+    "gtype": "gauge-34",
+    "gstyle": "Rounded",
+    "title": "Fill",
+    "units": "%",
+    "prefix": "",
+    "suffix": "%",
+    "min": 0,
+    "max": 100,
+    "segments": [
+      {
+        "color": "#f44336",
+        "from": 0
+      },
+      {
+        "color": "#ff9800",
+        "from": 10
+      },
+      {
+        "color": "#4caf50",
+        "from": 30
+      },
+      {
+        "color": "#ff9800",
+        "from": 80
+      },
+      {
+        "color": "#f44336",
+        "from": 95
+      }
+    ],
+    "width": 3,
+    "height": 4,
+    "order": 2,
+    "icon": "water_drop",
+    "sizeGauge": 20,
+    "sizeGap": 2,
+    "sizeSegments": 10,
+    "x": 1160,
+    "y": 760,
+    "wires": []
+  },
   {
     "id": "ui_ps_direction",
     "type": "ui-text",