fix: responsive layout for 360px minimum viewport width

- Store badges: w-full on mobile, sm:w-[260px] on larger screens
- AppPreview phone: w-full with aspect-ratio on mobile
- UseCases rows: stack vertically on mobile (flex-col sm:flex-row)
- Footer/DownloadCTA: responsive padding and container widths

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/DownloadCTA.astro

@@ -30,7 +30,7 @@ const phoneArt = "/assets/cta-phone-art.png";
       </div>
 
       <!-- Store badges -->
-      <div class="flex flex-wrap gap-[16px] items-center overflow-clip shrink-0">
+      <div class="flex flex-wrap gap-[16px] items-center overflow-clip shrink-0 w-full">
         <div class="bg-[#f28a4b] border border-[#c5834e] flex gap-[8px] h-[70px] items-center overflow-clip px-[16px] py-[12px] rounded-[20px] w-full sm:w-[260px] shrink-0">
           <img alt="Android" class="block shrink-0 size-[44px]" src={androidIcon} />
           <div class="flex flex-col gap-[3px] items-start overflow-clip shrink-0 whitespace-nowrap">