docs: fix stale milla-jovovich org URLs in website and plugin manifests (#787)

Follow-up to #766 which covers version.py, pyproject.toml, README,
CHANGELOG, and CONTRIBUTING. These 11 files still had the old org
name in URLs:

- website/ (VitePress config + 6 docs pages)
- .claude-plugin/ (plugin.json repository, README marketplace command)
- .codex-plugin/ (plugin.json URLs, README links)

Author name fields are intentionally unchanged.

website/index.md

@@ -17,7 +17,7 @@ hero:
       link: /concepts/the-palace
     - theme: alt
       text: GitHub ↗
-      link: https://github.com/milla-jovovich/mempalace
+      link: https://github.com/MemPalace/mempalace
 
 features:
   - icon: