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/frost.js

@@ -1,6 +1,6 @@
 const config = window.SeasonalsPluginConfig?.Frost || {};
 
-const frost = config.EnableFrost !== undefined ? config.EnableFrost : true;
+const frost = config.EnableFrost !== undefined ? config.EnableFrost : true; // enable/disable frost
 
 let msgPrinted = false;