Refresh docs for current client and Starling

[SetZero]

Summary

• Update user and server guidance for the current Nebula client and Starling services.
• Refresh getting-started and community screenshots, with sample users who have distinct avatars, banners, bios, and interests.
• Add downloadable sample profile art for cats, dogs, cars, anime, manga, K-pop, comics, and flowers, including three anime banner variants.
• Replace the dense flower example with a sparse arrangement and add an interactive community profile scene.

Verification

• npm run build completed (61 pages).
• Browser checks verified all ten profile choices and all five community banner switches.
• The community screenshot was captured from the rendered example at 1280 × 720.

Merging to main triggers the GitHub Pages deployment.