* M23 seen as Rwanda proxy facing U.N. African brigade
* Kigali's economic "miracle" may be at risk
* Fighting in mineral-rich east Congo keeps millions poor
* Ordinary Rwandans fret about deeper conflict
By Jenny Clover
KIGALI, Sept 5 (Reuters) - The deployment of a U.N. force of African troops in eastern Democratic Republic of Congo threatens to draw Rwanda into a damaging ...