Fix demo site auto-enhancement and content persistence

- Restructure demo directory from test-sites/ to demos/ with flattened layout
- Add auto-enhancement on server startup for all sites with auto_enhance: true
- Fix inconsistent content ID generation that prevented dan-eden-portfolio content persistence
- Update server configuration to enhance from source to separate output directories
- Remove manual enhancement from justfile in favor of automatic server enhancement
- Clean up legacy test files and unused restore command
- Update build system to use CDN endpoint instead of file copying

README.md

@@ -458,13 +458,11 @@ server:
       path: "/var/www/mysite"
       domain: "mysite.example.com"
       auto_enhance: true
-      backup_originals: true
     
     - site_id: "blog"
       path: "/var/www/blog"
       domain: "blog.example.com"
       auto_enhance: true
-      backup_originals: true
 ```
 
 ### **Quick Start**
@@ -493,7 +491,6 @@ server:
       path: "./demo-site"
       domain: "localhost:3000"
       auto_enhance: true
-      backup_originals: true
 
 # API configuration (for remote content API)
 api: