Replaced the static mermaid import in useMermaidInjector with a cached
dynamic import(). Also removed the mermaid manualChunks entry — it was
causing Rolldown to include the 841 kB (gzip) mermaid bundle in the
initial HTML modulepreload regardless of whether it was ever needed.
Mermaid now loads on-demand the first time a page with a diagram is viewed.

Vite now generates .gz files (level 9) for all JS and CSS assets after
each build. The Go router serves the pre-compressed variant with
Content-Encoding: gzip and Vary: Accept-Encoding when the client
supports it, falling back to uncompressed files otherwise. No CPU
overhead per request — compression is done once at build time.

…azy chunks

- Add spinner as Suspense fallback so lazy chunk load doesn't show a blank screen
- Set Vary: Accept-Encoding on the uncompressed static fallback path so caching
  proxies don't serve the wrong variant to gzip-capable clients
- Use base: './' in production builds so Vite emits relative asset paths;
  the preload-helper then resolves CSS/JS URLs via import.meta.url and correctly
  includes the runtime-configured sub-path (e.g. /wiki/) without any server-side
  string replacement - removes the now-redundant /static/ rewrite in router.go

Relative base ('./') broke SPA routing — the browser resolved asset URLs
relative to the current route URL instead of the document root.
Reverts to absolute paths (Vite default) with Go patching /static/ →
{basePath}/static/ in the HTML when a base path is configured.

… sub-path serving

With base: './' Vite generates ./static/... relative asset paths. Lazy
chunks resolve correctly at any base path via import.meta.url. Go rewrites
the initial ./static/ references in the HTML to absolute paths so they load
correctly when index.html is served for deep SPA routes. No <base> tag
needed — anchor hash navigation in page content stays unaffected.

Converts all 21 dialog components and the Search sidebar panel from eager
to lazy imports, reducing the main JS bundle from 503 kB to 346 kB (−31%).
Adds Suspense boundaries in DialogManager and Sidebar to support lazy rendering.

Extracts lazy() declarations from router.tsx and registries/index.tsx into
lazy-routes.tsx and lazy-dialogs.tsx respectively. Each new file exports
only components, satisfying the react-refresh/only-export-components rule.