Add WithMaxResponseBody option to prevent client-side OOM

Wraps response body with io.LimitedReader when configured, preventing
unbounded reads from io.ReadAll in Response.Bytes(). Protects against
upstream services returning unexpectedly large responses.

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

response.go

@@ -97,3 +97,18 @@ func (r *Response) BodyReader() io.Reader {
 	}
 	return r.Body
 }
+
+// limitedReadCloser wraps an io.LimitedReader with a separate Closer
+// so the original body can be closed.
+type limitedReadCloser struct {
+	R io.LimitedReader
+	C io.Closer
+}
+
+func (l *limitedReadCloser) Read(p []byte) (int, error) {
+	return l.R.Read(p)
+}
+
+func (l *limitedReadCloser) Close() error {
+	return l.C.Close()
+}