Update footer, resolution, and workflows

[arran4]

This PR addresses the following:

1. Updates the footer URL in generated images to point to the correct repo.
2. Increases the default resolution and DPI for better readability.
3. Removes the unnecessary Go cache step from the CI workflow.
4. Adds a new GitHub Action to automatically regenerate example images when changes are pushed to main.

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PR created automatically by Jules for task 6437565839418642723 started by @arran4

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[arran4]

ok