Add page visibility by group with centralized matrix

Introduce a Page Visibility Matrix that controls which pages each user
group can access, enforced in both frontend and backend:

Frontend:
- Create frontend/src/config/pageVisibility.js with PAGE_VISIBILITY
  matrix and canAccessPage() / getAccessiblePages() helpers
- NavDrawer: replace inline requiredGroups with canAccessPage() filter
- App.js: replace per-page isInGroup()/isAdmin() checks with generic
  route guard in setCurrentPage; remove VALID_PAGES constant
- localStorage validation: verify persisted page is accessible on load

Backend (page-level access enforcement):
- jiraTickets.js: add router-level requireGroup('Admin','Standard_User')
- archerTemplates.js: add router-level requireGroup('Admin','Standard_User')
- VCL multi-vertical already had requireGroup('Admin','Leadership')

Visibility matrix:
- Home, Knowledge Base: all groups
- Triage, Compliance, Exports: Admin, Standard_User, Leadership
- CCP Metrics: Admin, Leadership
- Jira, Archer Templates: Admin, Standard_User
- Admin Panel: Admin only
- Read_Only sees only Home and Knowledge Base

frontend/src/components/NavDrawer.js

@@ -1,12 +1,13 @@
 import React from 'react';
 import { X, Home, BarChart2, BookOpen, Download, ShieldCheck, Settings, Ticket, Building2, Layers } from 'lucide-react';
 import { useAuth } from '../contexts/AuthContext';
+import { canAccessPage } from '../config/pageVisibility';
 
 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', requiredGroups: ['Admin', 'Leadership'] },
+  { 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' },
@@ -16,7 +17,7 @@ const NAV_ITEMS = [
 const ADMIN_ITEM = { id: 'admin', label: 'Admin Panel', icon: Settings, color: '#EF4444', description: 'User management & audit' };
 
 export default function NavDrawer({ isOpen, onClose, currentPage, onNavigate }) {
-  const { isAdmin, isInGroup } = useAuth();
+  const { user } = useAuth();
 
   if (!isOpen) return null;
 
@@ -70,7 +71,7 @@ export default function NavDrawer({ isOpen, onClose, currentPage, onNavigate })
 
         {/* Nav items */}
         <nav style={{ display: 'flex', flexDirection: 'column', gap: '0.375rem' }}>
-          {NAV_ITEMS.filter(({ requiredGroups }) => !requiredGroups || isInGroup(...requiredGroups)).map(({ id, label, icon: Icon, color, description }) => {
+          {NAV_ITEMS.filter(item => canAccessPage(item.id, user?.group)).map(({ id, label, icon: Icon, color, description }) => {
             const active = currentPage === id;
             return (
               <button
@@ -124,8 +125,8 @@ export default function NavDrawer({ isOpen, onClose, currentPage, onNavigate })
             );
           })}
 
-          {/* Admin panel link — visible only to Admin group */}
-          {isAdmin() && (() => {
+          {/* Admin panel link — visible based on page visibility matrix */}
+          {canAccessPage('admin', user?.group) && (() => {
             const { id, label, icon: Icon, color, description } = ADMIN_ITEM;
             const active = currentPage === id;
             return (