feat: add pipeline observability and stats

.env.sample

@@ -88,3 +88,15 @@ CLICKHOUSE_SEND_RECEIVE_TIMEOUT_SECONDS=10
 
 BATCH_SIZE=1000
 BATCH_FLUSH_INTERVAL_SECONDS=2
+
+
+# =========================
+# Worker Observability
+# =========================
+
+WORKER_HTTP_HOST=0.0.0.0
+WORKER_HTTP_PORT=8001
+
+# API uses this while both services run directly on the host.
+WORKER_STATS_URL=http://localhost:8001/internal/stats
+WORKER_STATS_TIMEOUT_SECONDS=2