fix(widgets): add refetchInterval to WidgetDefinition for per-widget polling

The v1.69.0 caching refactor replaced Redis pub/sub with a global 30s
client polling interval. Live monitoring widgets (health-monitoring,
Dashdot, dns-hole) that previously refreshed every 5s were stuck at 30s.

Adds refetchInterval?: number | null to WidgetDefinition:
- number = poll every N seconds (e.g. 5 for live monitoring)
- null = fetch on mount only, no background polling
- undefined = use global 30s default

9 widgets set refetchInterval: 5 (live monitoring)
16 widgets set refetchInterval: null (slow data, mount-only)
Removed inline refetchInterval from docker widget component.

Fixes #6268

packages/widgets/src/system-resources/index.ts

@@ -14,6 +14,8 @@ const labelDisplayModeOptions = {
 
 export const { definition, componentLoader } = createWidgetDefinition("systemResources", {
   icon: IconGraphFilled,
+  queryKey: [["widget", "healthMonitoring"]],
+  refetchInterval: 5,
   supportedIntegrations: ["dashDot", "openmediavault", "truenas", "unraid", "glances", "synology"],
   createOptions() {
     return optionsBuilder.from((factory) => ({