perf: skip Next.js image re-optimization and stream proxy responses

Thumbnails are already optimized (WebP) by the API, so disable Next.js
image optimization to avoid redundant CPU work. Switch route handlers
from buffering (arrayBuffer) to streaming (response.body) to reduce
memory usage and latency.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/backoffice/app/api/books/[bookId]/thumbnail/route.ts

@@ -6,23 +6,22 @@ export async function GET(
   { params }: { params: Promise<{ bookId: string }> }
 ) {
   const { bookId } = await params;
-  
+
   try {
     const { baseUrl, token } = config();
     const response = await fetch(`${baseUrl}/books/${bookId}/thumbnail`, {
       headers: { Authorization: `Bearer ${token}` },
     });
-    
+
     if (!response.ok) {
-      return new NextResponse(`Failed to fetch thumbnail: ${response.status}`, { 
-        status: response.status 
+      return new NextResponse(`Failed to fetch thumbnail: ${response.status}`, {
+        status: response.status
       });
     }
-    
+
     const contentType = response.headers.get("content-type") || "image/webp";
-    const imageBuffer = await response.arrayBuffer();
-    
-    return new NextResponse(imageBuffer, {
+
+    return new NextResponse(response.body, {
       headers: {
         "Content-Type": contentType,
         "Cache-Control": "public, max-age=31536000, immutable",