audit: Tier 5.4 — wrap moveFolder cycle check + write in a tx

Concurrency-auditor HIGH: the cycle walk + UPDATE used to run as
separate statements. Two concurrent moves (A→B and B→A) could each
pass the walk against the pre-move tree and both write, leaving an
A↔B cycle. Whole sequence now runs inside one db.transaction().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/dashboard/widget-registry.tsx

@@ -40,8 +40,7 @@ const LeadSourceChart = dynamic(
   { loading: ChartFallback, ssr: false },
 );
 const OccupancyTimelineChart = dynamic(
-  () =>
-    import('./occupancy-timeline-chart').then((m) => ({ default: m.OccupancyTimelineChart })),
+  () => import('./occupancy-timeline-chart').then((m) => ({ default: m.OccupancyTimelineChart })),
   { loading: ChartFallback, ssr: false },
 );
 const PipelineFunnelChart = dynamic(