fix(website): SEO canonicals, host redirects, sitemap, app noindex

Addresses the high-volume issues from the Ahrefs audit:
- Worker entrypoint 301s every request not on https://paseo.sh
  (www subdomain and http variants), killing the duplicate-page
  errors and the HTTP→HTTPS internal-link notices.
- pageMeta() emits <link rel="canonical"> and og:url per route;
  every head() call now passes its canonical path.
- /blog stops rewriting itself to /blog?drafts=false; the search
  param only appears when explicitly true.
- Sitemap includes /blog and each post.
- Trim homepage title under SERP truncation, rewrite /agents meta
  description under 160 chars, pad short descriptions on
  /privacy, /download, /cloud, /changelog, /docs.
- app.paseo.sh gets <meta robots=noindex,nofollow> and a
  Disallow-all robots.txt so the SPA shell stops polluting the
  crawl with H1-missing / no-OG / low-word-count warnings.

packages/website/src/routes/download.tsx

@@ -18,12 +18,12 @@ import { useRelease } from "~/routes/__root";
 import "~/styles.css";
 
 export const Route = createFileRoute("/download")({
-  head: () => ({
-    meta: pageMeta(
-      "Download - Paseo",
-      "Download Paseo for macOS, Windows, Linux, iOS, and Android. Your dev environment, in your pocket.",
+  head: () =>
+    pageMeta(
+      "Download Paseo for macOS, Windows, Linux, iOS, and Android",
+      "Install Paseo on every platform. Native desktop apps for macOS, Windows, and Linux. Mobile apps for iOS and Android. Self-hosted, open source, free to download.",
+      "/download",
     ),
-  }),
   component: Download,
 });