Add monitoring service and database schema

- Implement monitoring service with heartbeat, lease tasks, resume tasks, and task result handling.
- Create monitoring time utilities for business date calculations.
- Add unit tests for date window resolution and business day handling.
- Define database schema for monitoring-related tables including quotas, daily reports, and task management.
- Establish migration scripts for creating and dropping monitoring tables.

server/migrations/20260410103000_create_monitoring_tables.down.sql

@@ -0,0 +1 @@
+DROP TABLE IF EXISTS tenant_monitoring_quotas;