docs: update TEKNISK_BESKRIVNING.md to reflect changes in authentication middleware and role-based access control; remove obsolete middleware.ts file

frontend/middleware.ts

@@ -1,19 +0,0 @@
-import { auth } from './auth';
-import { NextResponse } from 'next/server';
-
-export default auth((req) => {
-  const { pathname } = req.nextUrl;
-
-  if (pathname.startsWith('/admin')) {
-    const role = (req.auth?.user as any)?.role;
-    if (role !== 'admin') {
-      const loginUrl = new URL('/login', req.url);
-      loginUrl.searchParams.set('callbackUrl', pathname);
-      return NextResponse.redirect(loginUrl);
-    }
-  }
-});
-
-export const config = {
-  matcher: ['/admin/:path*'],
-};