task: #3616090 Set the RightUp logo and the site-template install image from the brand stylesheet

Issue: #3616090 Initialize the RightUp site template recipe and start the 1.0.x branch

Replaces the two placeholder brand images the recipe still carried, with assets taken from the RightUp brand stylesheet:

• logo.png — the RightUp wordmark, 512×512, transparent background (the flat chip background from the design is keyed out, corner alpha 0). Exported at 4× and scaled down, so it stays crisp.
• screenshot.webp — the site-template install image, 632×304, the size Varbase's "Choose a site template" step renders. Built from the brand share card: dark ground with the wordmark centred.

Nothing else changes: no recipe config, no content, no dependency.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release