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

demos/devigo-web/css/style.min.d8144fe26d70085d7ba48a72ae20106ac784ca57f9d48db3e57c8d7dd22b008a.css

@@ -0,0 +1,5 @@
+@import "tailwindcss";@plugin "@tailwindcss/forms";@plugin "@tailwindcss/typography";@plugin "./tailwind-plugin/tw-theme";@plugin "./tailwind-plugin/tw-bs-grid";@source "hugo_stats.json";@custom-variant dark (&:where(.dark,.dark *));@import "./safe.css";@import "./utilities.css";@layer base{@import "./base.css";
+}@layer components{@import "./components.css";
+  @import "./navigation.css";
+  @import "./buttons.css";
+}@import "search.css";@import "social-share.css";@import "gallery-slider.css";@import "images.css";@import "toc.css";@import "tab.css";@import "accordion.css";@import "modal.css";@import "notice.css";@import "module-overrides.css";@import "custom.css"