chore: add detailed logging to extract API route

Log upstream status, headers, and body preview to diagnose
Cloudflare 403 responses from Vercel deployment.

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

Author: toy-crane

app/api/extract/route.ts

@@ -9,28 +9,39 @@ export async function GET(request: NextRequest) {
     return NextResponse.json({ error: "url parameter is required" }, { status: 400 });
   }
 
+  const targetUrl = `${DEFUDDLE_API}/${url}`;
+
   try {
-    const response = await fetch(`${DEFUDDLE_API}/${url}`, {
+    const response = await fetch(targetUrl, {
       signal: AbortSignal.timeout(15_000),
       headers: {
         "User-Agent": request.headers.get("User-Agent") || "",
       },
     });
 
+    const body = await response.text();
+    const responseHeaders = Object.fromEntries(response.headers.entries());
+
+    console.log("[extract] upstream response", {
+      targetUrl,
+      status: response.status,
+      headers: responseHeaders,
+      bodyPreview: body.slice(0, 500),
+    });
+
     if (!response.ok) {
-      const text = await response.text();
-      return new NextResponse(text, {
+      return new NextResponse(body, {
         status: response.status,
         headers: { "Content-Type": response.headers.get("Content-Type") || "text/plain" },
       });
     }
 
-    const text = await response.text();
-    return new NextResponse(text, {
+    return new NextResponse(body, {
       status: 200,
       headers: { "Content-Type": response.headers.get("Content-Type") || "text/markdown" },
     });
-  } catch {
+  } catch (err) {
+    console.error("[extract] fetch error", { targetUrl, error: String(err) });
     return NextResponse.json({ error: "Failed to fetch the URL" }, { status: 502 });
   }
 }