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/Libraries/ActivityPub/Objects/NoteObject.php

@@ -34,9 +34,9 @@ class NoteObject extends ObjectType
     protected $inReplyTo;
 
     /**
-     * @var array
+     * @var string
      */
-    protected $replies = [];
+    protected $replies;
 
     /**
      * @param Note $note