refactor(dashboard): move price clients to app namespace and simplify data

app/Contracts/PriceClient.php

@@ -0,0 +1,12 @@
+<?php
+
+namespace App\Contracts;
+
+use Illuminate\Support\Collection;
+
+interface PriceClient
+{
+    public function getElectricityPrices(): Collection;
+
+    public function getGasPrices(): Collection;
+}