Fix energy dashboard redirect for device-consumption-only configs (#28322)

When users configure energy with only device consumption (no
grid/solar/battery/gas/water sources), the dashboard would redirect
to /config/energy instead of displaying. This occurred because
_generateLovelaceConfig() returned an empty views array.

The fix adds hasDeviceConsumption check and includes ENERGY_VIEW
when device consumption is configured, since energy-view-strategy
already supports device consumption cards.

src/panels/energy/ha-panel-energy.ts

@@ -268,8 +268,10 @@ class PanelEnergy extends LitElement {
       (source) => source.type === "gas"
     );
 
+    const hasDeviceConsumption = this._prefs.device_consumption.length > 0;
+
     const views: LovelaceViewConfig[] = [];
-    if (hasEnergy) {
+    if (hasEnergy || hasDeviceConsumption) {
       views.push(ENERGY_VIEW);
     }
     if (hasGas) {