Fix hashrate chart: auto-scale tooltip units, remove green block lines

- layout.pug: formatNetworkChartValue now calls scaleFromGH() for
  Hashrate labels instead of appending the fixed (GH/s) unit, so
  tooltip values match the Y-axis auto-scaled unit (MH/s…PH/s)
- custom.js: promote HASH_UNITS and scaleFromGH to global scope so
  layout.pug inline scripts can reuse them; fix unused 'mutations' param
- settings.json.tmpl: disable block_line on both charts (was green
  rgba(0,128,0)); color updated to purple rgba(120,60,220,0.25)

views/layout.pug

@@ -540,6 +540,15 @@ html(lang='en')
           return Math.floor(timestamp * 1000 / (60 * 1000)) * (60 * 1000);
         }
         function formatNetworkChartValue(val, roundDecimals, lbl, returnNum) {
+          if (returnNum)
+            return (val || 0);
+
+          if (lbl == 'Hashrate' && typeof scaleFromGH === 'function') {
+            var s = scaleFromGH(val || 0);
+            var dec = Math.abs(s.num) >= 100 ? 0 : Math.abs(s.num) >= 10 ? 1 : 2;
+            return s.num.toFixed(dec) + ' ' + s.unit;
+          }
+
           let max = 20;
 
           if (roundDecimals != -1)
@@ -551,10 +560,7 @@ html(lang='en')
               max = decimalCount;
           }
 
-          if (returnNum)
-            return (val || 0);
-          else
-            return Number((val || 0)).toLocaleString('en',{'minimumFractionDigits':0,'maximumFractionDigits':max,'useGrouping':true}) + (lbl == 'Hashrate' ? ' ' + getNetHashUnits() : '');
+          return Number((val || 0)).toLocaleString('en',{'minimumFractionDigits':0,'maximumFractionDigits':max,'useGrouping':true});
         }
         function populateHourChartData(result) {
           const roundedDataMap = new Map();