refactor: remove forum and topic feature chains

src/Credits/Credits.php

@@ -22,7 +22,7 @@ class Credits {
     }
 
     /**
-     * Alias used by forum unlock/purchase paths.
+     * Backward-compatible alias for credit spending.
      */
     public static function get_balance(int $user_id): int {
         return self::balance($user_id);