Bitesize Reading Library V4.9.2 — Discover fixes and YouTube links

- FIXED: Discover > Free now includes free resources from the shipped catalogue even when a live or saved catalogue omits them.
- FIXED: free detection now supports boolean/string flags, category labels and zero-price formats.
- FIXED: entering the Free category clears old search, grade, genre and hidden-owned filters so free resources appear immediately. Filters remain available for narrowing the results afterward.
- IMPROVED: Discover includes a dedicated YouTube section with the channel, channel video page and topic-search links.
- SUPPORTED: specific linked videos appear automatically when video IDs are provided in videos.json (or in the live video feed). The shipped video list is currently empty, so this update does not claim particular videos exist.
- NOTE: Internet connectivity is required to open YouTube and TPT listings. Always check current availability on the external site.

YouTube configuration: System/Data/videos.json; matching offline JavaScript: assets/videos.js.
To add individual videos, fill the videos array with records containing youtubeId, title, description and optional topics/keywords. Keep these two configurations in sync for distribution.
