fix(ui): display temperature graph times in local timezone

Configure ApexCharts to convert UTC timestamps to the browser's local
timezone for display. Previously, graph timestamps were shown in UTC
regardless of the container's TZ environment variable.

Fixes #30

Author: Starosdev

webapp/frontend/src/app/modules/dashboard/dashboard.component.ts

@@ -229,7 +229,10 @@ export class DashboardComponent implements OnInit, AfterViewInit, OnDestroy
                 }
             },
             xaxis: {
-                type: 'datetime'
+                type: 'datetime',
+                labels: {
+                    datetimeUTC: false
+                }
             }
         };
     }