Poll dispatch_due in the worker so scheduled posts fire.

Co-authored-by: Cursor <cursoragent@cursor.com>

.env.example

@@ -92,4 +92,7 @@ TIANJI_ENABLED=false
 TIANJI_TRACKER_URL=https://tianji.aimloperations.com/tracker.js
 TIANJI_WEBSITE_ID=cmshzhxdf6gee10qzkzrfn9iw
 
+# Worker poll interval for due scheduled campaigns / social posts (seconds).
+# DISPATCH_DUE_INTERVAL_SECONDS=15
+
 GUNICORN_WORKERS=2