feat: Set the engine stats interval to 1 s

The stats line carried throughput, KV usage and queue depth, but the
interval was never set. Unset, vLLM waits 10 s (vllm/envs.py:47), so a
quiet run looked idle for ten seconds and a short one printed nothing.

Export VLLM_LOG_STATS_INTERVAL in start.sh with a default of 1, and pass
it through Compose so .env can raise it back to 10. Add the variable to
.env.example, to the start.sh header, and to the Variables table in both
READMEs.

Co-Authored-By: Hinata <hinata@idihore.id>
Signed-off-by: MOVZX <movzx@yahoo.com>

docker-compose.yml

@@ -40,6 +40,7 @@ services:
       TOPO_TIMEOUT: ${TOPO_TIMEOUT:-20}
       GUARD: ${GUARD:-warn}
       COUNTERS: ${COUNTERS:-0}
+      VLLM_LOG_STATS_INTERVAL: ${VLLM_LOG_STATS_INTERVAL:-1}
       QWEN38_ABLITERATION: ${QWEN38_ABLITERATION:-Qwen3.8-Flash-Next-Uncensored}
     volumes:
       - "${MODEL_DIR:?Set MODEL_DIR in .env}:${MODEL_MOUNT_PATH:-/models/Qwen3.8-Flash-Next}:ro"