feat(site): prerender every locale and publish structured data, llms.txt and sitemaps

Crawlers received an empty client-rendered shell (107 characters of text);
most AI crawlers do not run JavaScript, so the product was invisible to them.

- Build renders each locale to static HTML (/ for Korean, /en/ … /vi/) with
  src/entry-server.tsx + scripts/prerender.mjs; the browser hydrates the same
  locale. The language menu links to those pages instead of switching in place.
- Per-locale head: title, description, canonical, hreflang (+ x-default /en/),
  Open Graph and X cards with a per-locale 1200x630 image.
- JSON-LD graph: Organization, WebSite, WebPage, SoftwareApplication (KRW
  offers, version, release date, download URL from the canonical sources),
  HowTo and FAQPage. No invented ratings.
- robots.txt (search, ai-input and ai-train allowed; /app, /api, invites
  excluded), sitemap.xml with language alternates, llms.txt and llms-full.txt
  generated from the same translations and canonical values.
- IndexNow key and a post-deploy ping (Bing, Naver, Yandex).
- A factual "at a glance" section and two FAQ answers (recognised languages,
  where data is stored) in all 10 languages.
- Icons, apple-touch-icon and web manifest; asset base is now absolute so
  sub-path pages load the same bundle.

Verified: 3.6k-7.7k characters of text per page, no hydration warnings,
no overflow at 320/1440 in six locales, axe 0, Lighthouse mobile SEO,
accessibility and best practices 100.

site/public/5d886cca4138946b8488203724b2f53d.txt

@@ -0,0 +1 @@
+5d886cca4138946b8488203724b2f53d

site/public/site.webmanifest

@@ -0,0 +1,15 @@
+{
+  "name": "D3RO Voice",
+  "short_name": "D3RO Voice",
+  "description": "Voice typing that runs on your PC — hold a key, speak, and the text is typed at your cursor.",
+  "start_url": "/",
+  "scope": "/",
+  "display": "browser",
+  "background_color": "#08090c",
+  "theme_color": "#08090c",
+  "icons": [
+    { "src": "/icons/icon-192.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "/icons/icon-512.png", "sizes": "512x512", "type": "image/png" },
+    { "src": "/icons/icon-maskable-512.png", "sizes": "512x512", "type": "image/png", "purpose": "maskable" }
+  ]
+}