fix(grafana): sync interval for CPU panels in main dashboard

- Change hardcoded "2m" interval to "$resolution" variable
- Affected panels: Global CPU Usage (id 77), CPU Usage (id 37)
- Ensures consistent refresh rate across all CPU metrics

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

grafana/dashboards/main.json

@@ -114,7 +114,7 @@
         "y": 1
       },
       "id": 77,
-      "interval": "2m",
+      "interval": "$resolution",
       "options": {
         "displayMode": "lcd",
         "legend": {
@@ -791,7 +791,7 @@
         "y": 9
       },
       "id": 37,
-      "interval": "2m",
+      "interval": "$resolution",
       "options": {
         "colorMode": "none",
         "graphMode": "none",