feat(docs-site): use the funk wordmark logo instead of "punktfunk" text

Swap the plain "punktfunk" text in the nav and landing hero for the real
brand wordmark from the marketing site. The source asset is a single
light-violet variant (made for dark surfaces), so it's painted as a CSS
mask and coloured per theme — deep-violet on light, light-violet on dark —
to stay legible with the docs' light/dark toggle.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs-site/src/routes/index.tsx

@@ -1,6 +1,7 @@
 import { createFileRoute, Link } from '@tanstack/react-router'
 import { HomeLayout } from 'fumadocs-ui/layouts/home'
 import BrandMark from '@/components/BrandMark'
+import Wordmark from '@/components/Wordmark'
 import { baseOptions } from '@/lib/layout.shared'
 
 export const Route = createFileRoute('/')({ component: Home })
@@ -10,7 +11,7 @@ function Home() {
     <HomeLayout {...baseOptions()}>
       <main className="flex flex-1 flex-col items-center justify-center gap-6 px-4 py-24 text-center">
         <BrandMark className="size-20 drop-shadow-[0_8px_30px_rgba(108,91,243,0.45)]" />
-        <h1 className="font-display text-4xl font-bold tracking-tight">punktfunk</h1>
+        <Wordmark className="h-12 md:h-14" />
         <p className="max-w-xl text-fd-muted-foreground">
           Linux-first, low-latency desktop and game streaming — a shared Rust protocol
           core with native clients per platform.