chore: remove showcase page (#3703)

## Summary
- Remove the Showcase page route, data, component, and all 175 showcase
images
- Remove "Showcase" from the navigation bar
- Keep the fresh-badge SVGs (still linked from external READMEs)

Also closed 12 open showcase PRs: #2691, #2861, #2846, #2720, #2282,
#2667, #2585, #1842, #2784, #1697, #2260, #2841.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartlomieju

www/components/Header.tsx

@@ -3,8 +3,6 @@ import NavigationBar from "./NavigationBar.tsx";
 export default function Header(props: { title: string; active: string }) {
   const isHome = props.active == "/";
   const isDocs = props.active == "/docs";
-  const isShowcase = props.active == "/showcase";
-
   return (
     <header
       class={[
@@ -13,7 +11,6 @@ export default function Header(props: { title: string; active: string }) {
         isDocs
           ? "h-20 max-w-screen-2xl w-full sticky top-0 bg-background-primary  z-50 backdrop-blur-xs"
           : "",
-        isShowcase ? "max-w-screen-xl w-full" : "",
       ].join(" ")}
       f-client-nav={false}
     >

www/components/NavigationBar.tsx

@@ -9,10 +9,6 @@ export default function NavigationBar(
       name: "Docs",
       href: "/docs",
     },
-    {
-      name: "Showcase",
-      href: "/showcase",
-    },
     {
       name: "Blog",
       href: "https://deno.com/blog?tag=fresh",