Refactor seasonal plugin configurations to improve clarity and consistency

- Updated comments for clarity on enabling/disabling features across various seasonal scripts.
- Changed default value checks to ensure undefined values are handled consistently.
- Enhanced readability by providing descriptive comments for configuration variables.

[skip ci]

Jellyfin.Plugin.Seasonals/Web/oktoberfest.js

@@ -1,5 +1,5 @@
 const config = window.SeasonalsPluginConfig?.Oktoberfest || {};
-const oktoberfest = config.EnableOktoberfest !== undefined ? config.EnableOktoberfest : true;
+const oktoberfest = config.EnableOktoberfest !== undefined ? config.EnableOktoberfest : true; // enable/disable oktoberfest
 
 const oktoberfestSymbols = ['🥨', '🍺', '🍻', '🥨', '🥨'];