docs: add Postgres migration plan and Kiro spec

- docs/guides/postgres-migration-plan.md: full migration manual with
  phases, port allocation, rollback plan, and timeline
- .kiro/specs/postgres-migration/: requirements, design, and tasks
- Replaces findings_json blob with individual indexed rows
- Enables per-BU closed counts via SQL queries
- Uses existing Postgres instance (port 5432), new cve_dashboard DB
- Testing on port 3003, cutover to 3001 with 30s downtime

frontend/src/components/pages/ReportingPage.js

@@ -5662,16 +5662,21 @@ export default function VulnerabilityTriagePage({ filterDate, filterEXC }) {
                 <div role="tabpanel">
                 {metricsTab === 'ivanti' && (
                 <div style={{ display: 'flex', gap: '3rem', flexWrap: 'wrap', alignItems: 'flex-start' }}>
-                    {/* Open vs Closed donut — open count from scoped findings, closed is global */}
+                    {/* Open vs Closed donut — open from scoped findings; closed only meaningful when unscoped */}
                     <div style={{ flex: '0 0 auto' }}>
                         <div style={{ fontFamily: 'monospace', fontSize: '0.68rem', fontWeight: '600', color: '#64748B', textTransform: 'uppercase', letterSpacing: '0.1em', marginBottom: '0.75rem' }}>
                             Open vs Closed
                         </div>
                         <StatusDonut
                             open={scopedFindings.length}
-                            closed={statusCounts.closed}
+                            closed={getActiveTeamsParam() ? 0 : statusCounts.closed}
                             loading={countsLoading}
                         />
+                        {getActiveTeamsParam() && (
+                            <div style={{ fontFamily: 'monospace', fontSize: '0.6rem', color: '#475569', marginTop: '0.5rem' }}>
+                                Closed count unavailable when filtered by BU
+                            </div>
+                        )}
                     </div>
 
                     {/* Divider */}