fix: update thumbnail style to match user requirements

[google-labs-jules]

This pull request updates the thumbnail.py script to better match the requested "Anime Flicker" style.

Key changes:

• Visuals: The poster image is now masked with a honeycomb pattern that has distinct, light-colored outlines, matching the reference image.
• Background: The background is now darker with fainter hex outlines.
• Fonts: Ensured correct font usage (Bebas Neue and Roboto).
• Cleanup: Removed hardcoded secrets and temporary files.

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PR created automatically by Jules for task 1981037527878897757 started by @botmaker00

[google-labs-jules]

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