refactor: add phpstan and update code to adhere to level 5

- move and refactor Image.php from Libraries to Entities folder
- update some database field names
/ types
- update composer packages

app/Controllers/Admin/HomeController.php

@@ -0,0 +1,18 @@
+<?php
+
+/**
+ * @copyright  2020 Podlibre
+ * @license    https://www.gnu.org/licenses/agpl-3.0.en.html AGPL3
+ * @link       https://castopod.org/
+ */
+
+namespace App\Controllers\Admin;
+
+class HomeController extends BaseController
+{
+    public function index()
+    {
+        session()->keepFlashdata('message');
+        return redirect()->route('podcast-list');
+    }
+}