Set up auto metric collection

Add Django Celery tasks and utilities to periodically collect system metrics (error rates, response times, queue sizes) and record them into metric_time_series. Include monitoring app scaffolding, metrics collector, Celery beat schedule, middleware for live metrics, and a Supabase edge function for cross-source metrics.

django/apps/monitoring/apps.py

@@ -0,0 +1,10 @@
+"""
+Monitoring app configuration.
+"""
+from django.apps import AppConfig
+
+
+class MonitoringConfig(AppConfig):
+    default_auto_field = 'django.db.models.BigAutoField'
+    name = 'apps.monitoring'
+    verbose_name = 'System Monitoring'