Use real meme template images instead of synthetic gradients

The generate_examples.py script now fetches blank template images from
the memegen GitHub repository (raw.githubusercontent.com) as a fallback
when the memegen API is unreachable.  This replaces the synthetic
colour gradients with the actual Buzz Lightyear, Doge, Drake, and
Distracted Boyfriend photos.

Three-tier resolution order:
1. memegen API (api.memegen.link)
2. GitHub raw content (raw.githubusercontent.com/jacebrowning/memegen)
3. Synthetic gradient (only for templates not in the GitHub repo)

The Distracted Boyfriend template uses custom text positions from the
memegen config.yml to place captions over each person correctly.
Only expanding-brain remains a gradient as it is not stored in the
memegen GitHub repository.

https://claude.ai/code/session_01MVwVedn97waTs89PBTnhzb

Author: claude