security: fix all Medium findings from FLAWS_REPORT audit

- Auth: TOTP replay protection with counter tracking, constant-time
  backup code comparison, atomic lockout increment, per-token logout
- Invoices/PDFs: net-based VAT calculation, dangerous URL scheme
  stripping in cleanQuillHtml, orders-pdf error handling
- Orders: reject item changes on status transition, cascading
  delete cleanup, take:1 with orderBy
- Projects: atomic rename collision handling, MIME/extension
  validation, empty customer name rejection
- Attendance: Czech public holiday awareness in frontend fund
  calculation, leave_hours 0 handling, invalid date NaN guard,
  bounded per-month queries in workfund
- Users/Admin: profile audit logging + password validation, session
  revocation guard, session ID validation, dashboard DB aggregation,
  soft-deleted record protection in scope templates
- Frontend: FormField label linkage, Pagination ARIA, error
  handling in OrderConfirmationModal, 401 propagation, GPS emoji
  hidden from screen readers, table sort state fix, geolocation
  race/abort cleanup, Leaflet popup DOM safety, Vehicles toggleActive
  minimal body, CompanySettings ref mutation fix, OfferDetail unlock
  abort, AttendanceBalances combined fetches
- Utils: env validation, Puppeteer concurrency mutex, invoice alert
  cron cleanup on shutdown, body limit alignment, TOTP error logging,
  trustProxy from env, symlink rejection, rate cache Map usage

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/routes/admin/invoices-pdf.ts

@@ -54,7 +54,14 @@ function cleanQuillHtml(html: string | null | undefined): string {
   );
   s = s.replace(/\s+on\w+\s*=\s*("[^"]*"|'[^']*'|[^\s>]*)/gi, "");
   s = s.replace(/\s+on\w+\s*=\s*[^\s>]*/gi, "");
-  s = s.replace(/href\s*=\s*["']?\s*javascript\s*:[^"'>\s]*/gi, 'href="#"');
+  s = s.replace(
+    /href\s*=\s*["']?\s*(javascript|data|vbscript)\s*:[^"'>\s]*/gi,
+    'href="#"',
+  );
+  s = s.replace(
+    /src\s*=\s*["']?\s*(javascript|data|vbscript)\s*:[^"'>\s]*/gi,
+    'src=""',
+  );
   s = s.replace(/( )/g, " ");
   s = s.replace(/\s+style\s*=\s*("[^"]*"|'[^']*'|[^\s>]*)/gi, "");
   let prev = "";