Add automated data retention cleanup

Implements edge function, Django tasks, and UI hooks/panels for automatic retention of old metrics, anomalies, alerts, and incidents, plus updates to query keys and monitoring dashboard to reflect data-retention workflows.

django/README_MONITORING.md

@@ -136,6 +136,24 @@ SELECT cron.schedule(
 );
 ```
 
+### 5. Data Retention Cleanup Setup
+
+The `data-retention-cleanup` edge function should run daily:
+
+```sql
+SELECT cron.schedule(
+  'data-retention-cleanup-daily',
+  '0 3 * * *', -- Daily at 3:00 AM
+  $$
+  SELECT net.http_post(
+    url:='https://api.thrillwiki.com/functions/v1/data-retention-cleanup',
+    headers:='{"Content-Type": "application/json", "Authorization": "Bearer YOUR_ANON_KEY"}'::jsonb,
+    body:=concat('{"time": "', now(), '"}')::jsonb
+  ) as request_id;
+  $$
+);
+```
+
 ## Metrics Collected
 
 ### Django Metrics
@@ -154,6 +172,35 @@ SELECT cron.schedule(
 - `submission_approval_rate`: Percentage of approved submissions (workflow)
 - `avg_moderation_time`: Average time to moderate in minutes (workflow)
 
+## Data Retention Policies
+
+The system automatically cleans up old data to manage database size:
+
+### Retention Periods
+- **Metrics** (`metric_time_series`): 30 days
+- **Anomaly Detections**: 30 days (resolved alerts archived after 7 days)
+- **Resolved Alerts**: 90 days
+- **Resolved Incidents**: 90 days
+
+### Cleanup Functions
+
+The following database functions manage data retention:
+
+1. **`cleanup_old_metrics(retention_days)`**: Deletes metrics older than specified days (default: 30)
+2. **`cleanup_old_anomalies(retention_days)`**: Archives resolved anomalies and deletes old unresolved ones (default: 30)
+3. **`cleanup_old_alerts(retention_days)`**: Deletes old resolved alerts (default: 90)
+4. **`cleanup_old_incidents(retention_days)`**: Deletes old resolved incidents (default: 90)
+5. **`run_data_retention_cleanup()`**: Master function that runs all cleanup operations
+
+### Automated Cleanup Schedule
+
+Django Celery tasks run retention cleanup automatically:
+- Full cleanup: Daily at 3:00 AM
+- Metrics cleanup: Daily at 3:30 AM
+- Anomaly cleanup: Daily at 4:00 AM
+
+View retention statistics in the Admin Dashboard's Data Retention panel.
+
 ## Monitoring
 
 View collected metrics in the Admin Monitoring Dashboard: