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/components/NavDrawer.js

@@ -1,11 +1,12 @@
 import React from 'react';
-import { X, Home, BarChart2, BookOpen, Download, ShieldCheck, Settings, Ticket } from 'lucide-react';
+import { X, Home, BarChart2, BookOpen, Download, ShieldCheck, Settings, Ticket, Building2 } from 'lucide-react';
 import { useAuth } from '../contexts/AuthContext';
 
 const NAV_ITEMS = [
   { id: 'home',           label: 'Home',           icon: Home,        color: '#0EA5E9', description: 'Main dashboard'            },
   { id: 'triage',         label: 'Vuln Triage',    icon: BarChart2,   color: '#F59E0B', description: 'Active findings & CVE triage' },
   { id: 'compliance',     label: 'Compliance',     icon: ShieldCheck, color: '#14B8A6', description: 'AEO posture & metrics'     },
+  { id: 'ccp-metrics',    label: 'CCP Metrics',    icon: Building2,   color: '#A78BFA', description: 'Cross-vertical VCL reporting' },
   { id: 'knowledge-base', label: 'Knowledge Base', icon: BookOpen,    color: '#10B981', description: 'Articles & documentation'   },
   { id: 'exports',        label: 'Exports',        icon: Download,    color: '#8B5CF6', description: 'Export data & reports'      },
   { id: 'jira',           label: 'Jira Tickets',   icon: Ticket,      color: '#6366F1', description: 'Jira issue tracking & sync' },