Add CCP Metrics page with multi-vertical VCL upload and cross-org reporting

New feature: multi-file per-vertical compliance xlsx upload with scoped
resolution logic, executive-level aggregated reporting, and drill-down
by vertical and metric. Supports daily upload cadence and batch commit.

Backend:
- Migration: add vertical column to compliance_items/uploads, create
  vcl_multi_vertical_summary table
- New route module: routes/vclMultiVertical.js with preview, commit,
  stats, trend, metric drill-down, device list, and burndown endpoints
- New helpers: parseVerticalFilename(), computeVerticalBurndown()
- Vertical-scoped resolution: uploading one vertical never resolves
  items from other verticals

Frontend:
- CCPMetricsPage with stats bar, trend chart, donut, vertical table
- Drill-down: vertical -> metrics by category -> device list
- Per-vertical burndown forecast chart
- MultiVerticalUploadModal: multi-file drag-drop, batch preview, commit
- Nav entry: CCP Metrics (Building2 icon)

Docs:
- Design brief for stakeholder meeting (docs/vcl-multi-vertical-design-brief.md)

frontend/src/App.js

@@ -14,6 +14,7 @@ import VulnerabilityTriagePage from './components/pages/ReportingPage';
 import KnowledgeBasePage from './components/pages/KnowledgeBasePage';
 import ExportsPage from './components/pages/ExportsPage';
 import CompliancePage from './components/pages/CompliancePage';
+import CCPMetricsPage from './components/pages/CCPMetricsPage';
 import JiraPage from './components/pages/JiraPage';
 import AdminPage from './components/pages/AdminPage';
 import ArchiveSummaryBar from './components/pages/ArchiveSummaryBar';
@@ -1082,6 +1083,7 @@ export default function App() {
         {/* Page content */}
         {currentPage === 'triage'         && <VulnerabilityTriagePage filterDate={calendarFilter} filterEXC={reportingExcFilter} />}
         {currentPage === 'compliance'     && <CompliancePage onNavigate={setCurrentPage} />}
+        {currentPage === 'ccp-metrics'    && <CCPMetricsPage />}
         {currentPage === 'knowledge-base' && <KnowledgeBasePage />}
         {currentPage === 'exports'        && <ExportsPage />}
         {currentPage === 'jira'           && <JiraPage />}