fix(status): update status display to use action-based thresholds

The status command was still trying to access ups.thresholds.battery which
no longer exists in v4.1+ configs. Thresholds are now in the actions array.

Changes:
- Updated displaySingleUpsStatus() to get thresholds from actions
- Finds first action with thresholds defined for battery symbol display
- Shows success/warning symbol only if threshold is defined

This fixes 'Cannot read properties of undefined (reading battery)' error
when running nupst status on v4.1+ configs.

ts/systemd.ts

@@ -330,7 +330,16 @@ WantedBy=multi-user.target
 
       // Display battery with color coding
       const batteryColor = getBatteryColor(status.batteryCapacity);
-      const batterySymbol = status.batteryCapacity >= ups.thresholds.battery ? symbols.success : symbols.warning;
+
+      // Get threshold from actions (if any action has thresholds defined)
+      const actionWithThresholds = ups.actions?.find((action: any) => action.thresholds);
+      const batteryThreshold = actionWithThresholds?.thresholds?.battery;
+      const batterySymbol = batteryThreshold !== undefined && status.batteryCapacity >= batteryThreshold
+        ? symbols.success
+        : batteryThreshold !== undefined
+        ? symbols.warning
+        : '';
+
       logger.log(`    Battery: ${batteryColor(status.batteryCapacity + '%')} ${batterySymbol}  Runtime: ${getRuntimeColor(status.batteryRuntime)(status.batteryRuntime + ' min')}`);
 
       // Display host info