test: increase timeouts for consumer group operations in E2E tests

Consumer group operations (coordinator discovery, offset fetch/commit) are
slower in CI environments with limited resources. This increases timeouts to:
- ProduceMessages: 10s -> 30s (for when consumer groups are active)
- ConsumeWithGroup: 30s -> 60s (for offset fetch/commit operations)

Fixes the TestOffsetManagement timeout failures in GitHub Actions CI.

test/kafka/internal/testutil/clients.go

@@ -84,7 +84,9 @@ func (k *KafkaGoClient) ProduceMessages(topicName string, messages []kafka.Messa
 	}
 	defer writer.Close()
 
-	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	// Increased timeout to handle slow CI environments, especially when consumer groups
+	// are active and holding locks or requiring offset commits
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
 	err := writer.WriteMessages(ctx, messages...)
@@ -144,7 +146,9 @@ func (k *KafkaGoClient) ConsumeWithGroup(topicName, groupID string, expectedCoun
 	offset := reader.Offset()
 	k.t.Logf("Consumer group reader created for group %s, initial offset: %d", groupID, offset)
 
-	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	// Increased timeout for consumer groups - they require coordinator discovery,
+	// offset fetching, and offset commits which can be slow in CI environments
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
 	defer cancel()
 
 	var messages []kafka.Message