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

app/Contracts/PriceRepository.php

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