chore: remove showcase page (freshframework#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: freshframework#2691, freshframework#2861, freshframework#2846, freshframework#2720, freshframework#2282,
freshframework#2667, freshframework#2585, freshframework#1842, freshframework#2784, freshframework#1697, freshframework#2260, freshframework#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",