docs(site): consolidate landing page and add macOS download

Publish one bilingual download surface with clearly separated iPhone/iPad App Store and notarized Mac DMG actions.

docs/sitemap.xml

@@ -3,40 +3,13 @@
         xmlns:xhtml="http://www.w3.org/1999/xhtml">
   <url>
     <loc>https://hkgood.github.io/OSGKeyboard/</loc>
-    <lastmod>2026-07-29</lastmod>
+    <lastmod>2026-07-30</lastmod>
     <changefreq>weekly</changefreq>
     <priority>1.0</priority>
     <xhtml:link rel="alternate" hreflang="zh-Hans" href="https://hkgood.github.io/OSGKeyboard/"/>
-    <xhtml:link rel="alternate" hreflang="en" href="https://hkgood.github.io/OSGKeyboard/en/"/>
+    <xhtml:link rel="alternate" hreflang="en" href="https://hkgood.github.io/OSGKeyboard/?lang=en"/>
     <xhtml:link rel="alternate" hreflang="x-default" href="https://hkgood.github.io/OSGKeyboard/"/>
   </url>
-  <url>
-    <loc>https://hkgood.github.io/OSGKeyboard/en/</loc>
-    <lastmod>2026-07-29</lastmod>
-    <changefreq>weekly</changefreq>
-    <priority>0.95</priority>
-    <xhtml:link rel="alternate" hreflang="zh-Hans" href="https://hkgood.github.io/OSGKeyboard/"/>
-    <xhtml:link rel="alternate" hreflang="en" href="https://hkgood.github.io/OSGKeyboard/en/"/>
-    <xhtml:link rel="alternate" hreflang="x-default" href="https://hkgood.github.io/OSGKeyboard/"/>
-  </url>
-  <url>
-    <loc>https://hkgood.github.io/OSGKeyboard/install/</loc>
-    <lastmod>2026-07-29</lastmod>
-    <changefreq>monthly</changefreq>
-    <priority>0.85</priority>
-  </url>
-  <url>
-    <loc>https://hkgood.github.io/OSGKeyboard/compare/</loc>
-    <lastmod>2026-07-29</lastmod>
-    <changefreq>monthly</changefreq>
-    <priority>0.85</priority>
-  </url>
-  <url>
-    <loc>https://hkgood.github.io/OSGKeyboard/mac-dictation/</loc>
-    <lastmod>2026-07-29</lastmod>
-    <changefreq>monthly</changefreq>
-    <priority>0.8</priority>
-  </url>
   <url>
     <loc>https://hkgood.github.io/OSGKeyboard/privacy/</loc>
     <lastmod>2026-07-29</lastmod>