fix(website): fetch release version at runtime with asset validation

Move release version resolution from build-time (vite.config.ts) to
runtime (server function on Cloudflare Workers). The server function
fetches GitHub releases, filters out prereleases/drafts, and only
returns a version that has all required assets (Mac DMG, Linux AppImage,
Windows exe). Uses Cloudflare's cf.cacheEverything with a 60s TTL to
avoid hitting GitHub on every request.

This fixes a race condition where the website would deploy and show
download links for a new release before the desktop build assets were
actually uploaded, resulting in 404s for users.

packages/website/src/components/landing-page.tsx

@@ -6,13 +6,14 @@ import {
   appStoreUrl,
   playStoreUrl,
   webAppUrl,
-  downloadOptions,
+  getDownloadOptions,
   useDetectedPlatform,
   AppleIcon,
   AndroidIcon,
   TerminalIcon,
   GlobeIcon,
 } from "~/downloads";
+import { useRelease } from "~/routes/__root";
 import { Mic } from "lucide-react";
 import { HeroMockup } from "~/components/hero-mockup";
 import { ClaudeIcon } from "~/components/mockup";
@@ -772,8 +773,9 @@ function GetStarted() {
 }
 
 function DownloadButton() {
+  const { version } = useRelease();
   const detectedPlatform = useDetectedPlatform();
-  const primary = downloadOptions.find((o) => o.platform === detectedPlatform)!;
+  const primary = getDownloadOptions(version).find((o) => o.platform === detectedPlatform)!;
   const PrimaryIcon = primary.icon;
 
   return (