generate gif thumbnail

[eufelipemateus]

Description

This PR adds an asynchronous Job that automatically generates a thumbnail for GIF files.

✅ This enhancement resolves an issue where certain parts of the system could not properly display GIF content due to the lack of a preview thumbnail.

Fixed issues:

• #6021: Legacy UI failed to render GIF content correctly.
• Admin panel: Media list showed raw GIFs without preview thumbnails.

With this Job, GIFs will now automatically have a static preview image, ensuring:

• Better compatibility.
• Improved system performance.
• More consistent user experience.

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Summary of changes:

• Added new Job for GIF thumbnail generation.
• Uses pbmedia/laravel-ffmpeg for frame extraction.
• Automatically updates the media model with thumbnail_path.