Add Container component and fix radius/maxWidth theming

- Drop buttonRadius prop; button now uses --radius via rounded-md
- Inject @theme radius mappings into ThemeProvider so rounded-* utilities
  pick up --radius inside the Tailwind CDN iframe
- Add shared Container that consumes --container-max-width set from the
  global maxWidth prop, replacing ad-hoc "container mx-auto max-w-7xl px-6"
  wrappers across commerce, landing, footer, navigation, and others
- Simplify maxWidth options to Small/Medium/Large/X-Large/Full bleed and
  shift the scale up so Large (1280px) matches the previous default

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

components/footer/footer.tsx

@@ -1,6 +1,7 @@
 import { useState } from "react";
 import { Link } from "react-router";
 import { Typography } from "@/components/Typography";
+import { Container } from "@/components/layout/Container";
 
 export type FooterProps = {
   brand: string;
@@ -45,7 +46,7 @@ export function Footer({
 
   return (
     <footer className="border-t border-border bg-background">
-      <div className="container mx-auto max-w-7xl px-6 py-20 md:py-24">
+      <Container className="py-20 md:py-24">
         <div className="grid grid-cols-1 gap-12 md:grid-cols-12">
           <div className="md:col-span-4">
             <Typography variant="h5" as="p">
@@ -123,7 +124,7 @@ export function Footer({
             ))}
           </div>
         </div>
-      </div>
+      </Container>
     </footer>
   );
 }