Add comprehensive Matrix alerting system with Grafana integration

- Implement custom Python alerting system (src/alerting.py) with water level monitoring, data freshness checks, and Matrix notifications
- Add complete Grafana Matrix alerting setup guide (docs/GRAFANA_MATRIX_SETUP.md) with webhook configuration, alert rules, and notification policies
- Create Matrix quick start guide (docs/MATRIX_QUICK_START.md) for rapid deployment
- Integrate alerting commands into main application (--alert-check, --alert-test)
- Add Matrix configuration to environment variables (.env.example)
- Update Makefile with alerting targets (alert-check, alert-test)
- Enhance status command to show Matrix notification status
- Support station-specific water level thresholds and escalation rules
- Provide dual alerting approach: native Grafana alerts and custom Python system

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

.env.example

@@ -82,6 +82,18 @@ SMTP_PORT=587
 SMTP_USERNAME=
 SMTP_PASSWORD=
 
+# Matrix Alerting Configuration
+MATRIX_HOMESERVER=https://matrix.org
+MATRIX_ACCESS_TOKEN=
+MATRIX_ROOM_ID=
+
+# Grafana Integration
+GRAFANA_URL=http://localhost:3000
+
+# Alert Configuration
+ALERT_MAX_AGE_HOURS=2
+ALERT_CHECK_INTERVAL_MINUTES=15
+
 # Development Settings
 DEBUG=false
 DEVELOPMENT_MODE=false