EFV third-party m3u8 hosting of M3U8 with CMS/APP previews, improved VBR and BUG fixes

This sounds simple but is complex to implement. Playing third-party m3u8 only requires storing it in the database, but seamlessly integrating route-level previews in the CMS and APP requires locally hosting the m3u8 and processing all m3u8 requests as middleware. We also improved VBR, variable-bitrate constraints, from 10% to 50%, and fixed duplicate data returned by the intelligent recommendation API.

Updates

• One: Added third-party m3u8 import. Retrieve metadata from a Douban link, enter the m3u8 URL and save.
• Two: The system detects whether third-party m3u8 is adaptive m3u8 or ordinary m3u8, and whether the m3u8 uses absolute or relative paths, fetches the m3u8 content and saves a local M3u8. It then uses FluentAPI to generate screenshots and animations and sets a poster automatically. Route-level permission-based previews work in the frontend CMS and APP.
• Three: Improved VBR constraints from 10% to 50%. For 720:1000, the output is 720P at average bitrate 1000. Previously, a 10% maximum constraint meant 1100; with 50%, it becomes 1500. The program dynamically allocates bitrate, improving image quality in moving scenes.
• Four: Fixed duplicate data in intelligent recommendation API responses, reported after the previous recommendation API update.