Add weekly progress and validation

app/Models/Category.php

@@ -1,4 +1,4 @@
-<?php
+<?php
 
 class Category
 {
@@ -8,4 +8,12 @@ class Category
             ->query('SELECT id, name, color FROM categories ORDER BY name')
             ->fetchAll();
     }
+
+    public static function exists(int $id): bool
+    {
+        $statement = Database::connection()->prepare('SELECT id FROM categories WHERE id = :id LIMIT 1');
+        $statement->execute(['id' => $id]);
+
+        return (bool) $statement->fetch();
+    }
 }