Add weekly vulnerability report upload feature

Implements a comprehensive system for uploading and processing weekly
vulnerability reports that automatically splits multiple CVE IDs in a
single cell into separate rows for easier filtering and analysis.

Backend Changes:
- Add weekly_reports table with migration
- Create Excel processor helper using Python child_process
- Implement API routes for upload, list, download, delete
- Mount routes in server.js after multer initialization
- Move split_cve_report.py to backend/scripts/

Frontend Changes:
- Add WeeklyReportModal component with phase-based UI
- Add "Weekly Report" button next to NVD Sync
- Integrate modal into App.js with state management
- Display existing reports with current report indicator
- Download buttons for original and processed files

Features:
- Upload .xlsx files (editor/admin only)
- Automatic CVE ID splitting via Python script
- Store metadata in database + files on filesystem
- Auto-archive previous reports (mark one as current)
- Download both original and processed versions
- Audit logging for all operations
- Security: file validation, auth checks, path sanitization

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/App.js

@@ -6,6 +6,7 @@ import UserMenu from './components/UserMenu';
 import UserManagement from './components/UserManagement';
 import AuditLog from './components/AuditLog';
 import NvdSyncModal from './components/NvdSyncModal';
+import WeeklyReportModal from './components/WeeklyReportModal';
 import './App.css';
 
 const API_BASE = process.env.REACT_APP_API_BASE || 'http://localhost:3001/api';
@@ -173,6 +174,7 @@ export default function App() {
   const [showUserManagement, setShowUserManagement] = useState(false);
   const [showAuditLog, setShowAuditLog] = useState(false);
   const [showNvdSync, setShowNvdSync] = useState(false);
+  const [showWeeklyReport, setShowWeeklyReport] = useState(false);
   const [newCVE, setNewCVE] = useState({
     cve_id: '',
     vendor: '',
@@ -757,6 +759,15 @@ export default function App() {
                   NVD Sync
                 </button>
               )}
+              {canWrite() && (
+                <button
+                  onClick={() => setShowWeeklyReport(true)}
+                  className="intel-button intel-button-success relative z-10 flex items-center gap-2"
+                >
+                  <Upload className="w-4 h-4" />
+                  Weekly Report
+                </button>
+              )}
               {canWrite() && (
                 <button
                   onClick={() => setShowAddCVE(true)}
@@ -810,6 +821,11 @@ export default function App() {
           <NvdSyncModal onClose={() => setShowNvdSync(false)} onSyncComplete={() => fetchCVEs()} />
         )}
 
+        {/* Weekly Report Modal */}
+        {showWeeklyReport && (
+          <WeeklyReportModal onClose={() => setShowWeeklyReport(false)} />
+        )}
+
         {/* Add CVE Modal */}
         {showAddCVE && (
           <div className="fixed inset-0 modal-overlay flex items-center justify-center z-50 p-4">