Emit self-hosted fonts by importing from JS, not CSS @import

Firefox's console was spammed with "downloadable font: download failed
status=2147746065" for every @fontsource family — Inter, Alfa Slab One,
JetBrains Mono. Root cause: the built CSS referenced
./files/inter-latin-400-normal.woff2 but no font files were ever emitted
to build/client/_app/immutable/assets/.

Vite's CSS `@import` inlines the imported file's *text* but doesn't
crawl the resulting url() references to emit their assets. Since
tokens.css was doing `@import '@fontsource/inter/400.css'` and being
pulled into +layout.svelte via a Svelte <style> @import, the fonts
lived entirely in CSS space where Vite's asset emission never saw them.

Moved the @fontsource imports into src/lib/ui/styles/fonts.ts and
side-effect-import that module from +layout.svelte's <script>. JS
imports go through the module graph, so Vite walks the CSS, sees the
url() references, and emits the woff/woff2 binaries.

Verified: build now emits 80 font files (14 subsets × 5-6 weights)
into build/client/_app/immutable/assets/ and the CSS url()s resolve
to the correct hashed filenames in the same directory.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/routes/+layout.svelte

@@ -4,6 +4,9 @@
     import { startServerStream } from '$ui/stores/servers.js';
     import { page } from '$app/stores';
     import BrandMark from '$ui/components/BrandMark.svelte';
+    // Side-effect import — puts @fontsource CSS on Vite's module graph so
+    // the referenced woff/woff2 files get emitted into the build.
+    import '$ui/styles/fonts.js';
 
     interface Props { children: import('svelte').Snippet }
     let { children }: Props = $props();