Fix NameError and add feature flag for scheduler

- Restored start_scheduler() function that was missing
- Added DISABLE_SCHEDULER feature flag check in main()
- App should start now without scheduler running
- Fixed 500 Internal Server Error

russell@unturf.com is the boss

app.py

@@ -889,6 +889,23 @@ def check_and_run_scheduler():
         log.error(f"On-demand scheduler error: {e}")
 
 
+def start_scheduler():
+    """Start the background scheduler."""
+    global scheduler_thread, scheduler_running
+    
+    # Check if scheduler is disabled via environment variable
+    disable_scheduler = os.environ.get('DISABLE_SCHEDULER', '').lower() in ('true', '1', 'yes')
+    if disable_scheduler:
+        log.info("Scheduler disabled by DISABLE_SCHEDULER environment variable")
+        return
+    
+    if not scheduler_running:
+        scheduler_running = True
+        scheduler_thread = threading.Thread(target=scheduler_worker, daemon=True)
+        scheduler_thread.start()
+        log.info("Scheduler started")
+
+
 def stop_scheduler():
     """Stop the background scheduler."""
     global scheduler_thread, scheduler_running
@@ -2313,8 +2330,12 @@ def main(*config, **settings):
 
     config.scan()
 
-    # Start the scheduler
-    start_scheduler()
+    # Start the scheduler (with feature flag)
+    disable_scheduler = os.environ.get('DISABLE_SCHEDULER', '').lower() in ('true', '1', 'yes')
+    if not disable_scheduler:
+        start_scheduler()
+    else:
+        log.info("Scheduler disabled by DISABLE_SCHEDULER environment variable")
 
     return config.make_wsgi_app()