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/internal/tenant/app/media_service.go

@@ -288,6 +288,10 @@ func (s *MediaService) RegisterPluginInstallation(ctx context.Context, req Regis
 		}
 	}
 
+	if err := ensureMonitoringPrimaryInstallation(ctx, tx, actor.TenantID, installationID); err != nil {
+		return nil, err
+	}
+
 	if err := tx.Commit(ctx); err != nil {
 		return nil, response.ErrInternal(50065, "installation_commit_failed", "failed to commit plugin installation")
 	}
@@ -300,6 +304,21 @@ func (s *MediaService) RegisterPluginInstallation(ctx context.Context, req Regis
 	}, nil
 }
 
+func ensureMonitoringPrimaryInstallation(ctx context.Context, tx pgx.Tx, tenantID, installationID int64) error {
+	if _, err := tx.Exec(ctx, `
+		INSERT INTO tenant_monitoring_quotas (
+			tenant_id, primary_installation_id
+		)
+		VALUES ($1, $2)
+		ON CONFLICT (tenant_id) DO UPDATE
+		SET primary_installation_id = COALESCE(tenant_monitoring_quotas.primary_installation_id, EXCLUDED.primary_installation_id),
+			updated_at = NOW()
+	`, tenantID, installationID); err != nil {
+		return response.ErrInternal(50068, "monitoring_quota_update_failed", "failed to assign monitoring plugin installation")
+	}
+	return nil
+}
+
 func (s *MediaService) ListPlatformAccounts(ctx context.Context) ([]PlatformAccountResponse, error) {
 	actor := auth.MustActor(ctx)
 	rows, err := s.pool.Query(ctx, `