Fix download route params for Next.js 15 - must await params

app/api/download/[template]/route.ts

@@ -7,10 +7,10 @@ import { readdir, stat } from 'fs/promises'
 
 export async function GET(
   request: NextRequest,
-  { params }: { params: { template: string } }
+  { params }: { params: Promise<{ template: string }> }
 ) {
   try {
-    const templateId = params.template
+    const { template: templateId } = await params
     const template = templates.find(t => t.id === templateId)
 
     if (!template || !template.downloadable) {