Migrate to Chi router and add Norwegian Devigo demo

Major improvements:
- Replace Gorilla Mux with Chi v5 router for better performance and cleaner code
- Fix CSS/JS MIME type issues that prevented proper asset loading
- Add built-in CORS middleware replacing manual OPTIONS handlers
- Simplify routing with nested route syntax
- Update URL parameter extraction from mux.Vars to chi.URLParam

New Devigo demo:
- Add production Norwegian sales training website (devigo.no)
- Real-world Hugo-generated content with TailwindCSS
- 39 insertr-enhanced elements for comprehensive CMS testing
- Demonstrates international language support and B2B use cases
- Fixed asset paths for localhost serving compatibility

Technical benefits:
- Automatic MIME type detection for static files
- Reduced code complexity with built-in middleware
- Better performance with lighter dependency stack
- Production-ready CORS handling

insertr.yaml

@@ -15,22 +15,22 @@ server:
     - site_id: "default"
       path: "./demos/default_enhanced"
       source_path: "./demos/default"
-      domain: "localhost:3000"
       auto_enhance: true
     - site_id: "simple"
       path: "./demos/simple_enhanced"
       source_path: "./demos/simple"
-      domain: "localhost:3000"
       auto_enhance: true
     - site_id: "dan-eden-portfolio"
       path: "./demos/dan-eden-portfolio_enhanced"
       source_path: "./demos/dan-eden-portfolio"
-      domain: "localhost:3000"
+      auto_enhance: true
+    - site_id: "devigo-web"
+      path: "./demos/devigo-web_enhanced"
+      source_path: "./demos/devigo-web"
       auto_enhance: true
     # Example additional site configuration:
     # - site_id: "mysite"
     #   path: "/var/www/mysite"
-    #   domain: "mysite.example.com"
     #   auto_enhance: true