Configure ETERNITY_LOOP_INTERVAL via environment variable

backend.py

@@ -1716,7 +1716,8 @@ def run_eternity_loop():
                 loop = asyncio.new_event_loop()
                 loop.run_until_complete(execute_eternity_cycle(goal))
                 loop.close()
-                time.sleep(43200) # 12 hours
+                interval = int(os.environ.get("ETERNITY_LOOP_INTERVAL", "3600"))
+                time.sleep(interval)
                 
         except Exception as e:
             log_activity(f"[Eternity Loop Error] Loop crash: {e}")