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

demos/dan-eden-portfolio/insertr-config.json

@@ -0,0 +1,22 @@
+{
+  "site_name": "Dan Eden Portfolio",
+  "description": "Personal portfolio site with clean design and minimal styling",
+  "base_url": "https://daneden.me",
+  "content_sections": [
+    {
+      "selector": ".home_xxl__iX0Z1",
+      "type": "markdown",
+      "editable": true,
+      "description": "Main bio paragraph - Product Designer intro"
+    },
+    {
+      "selector": "span.insertr",
+      "type": "text",
+      "editable": true,
+      "description": "Various text content elements (company, descriptions, titles)"
+    }
+  ],
+  "css_frameworks": ["Next.js CSS Modules"],
+  "complexity": "simple",
+  "testing_notes": "Clean Next.js site with CSS modules. Good test for CSS-in-JS compatibility and semantic HTML structure."
+}