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

cmd/enhance.go

@@ -51,7 +51,7 @@ func runEnhance(cmd *cobra.Command, args []string) {
 	outputDir := viper.GetString("cli.output")
 
 	// Auto-derive site_id for demo paths or validate for production
-	if strings.Contains(inputDir, "/demos/") {
+	if strings.Contains(inputDir, "/demos/") || strings.Contains(inputDir, "./demos/") {
 		// Auto-derive site_id from demo path
 		siteID = content.DeriveOrValidateSiteID(inputDir, siteID)
 	} else {