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/auth.ts

@@ -153,11 +153,32 @@ export default async function authRoutes(
         return error(reply, "Uživatel nenalezen", 401);
       }
 
-      const isValid = OTPAuth.verify(user.totp_secret, totp_code);
-      if (!isValid) {
+      const verifyResult = OTPAuth.verify(user.totp_secret, totp_code);
+      if (!verifyResult.valid) {
         return error(reply, "Neplatný TOTP kód", 401);
       }
 
+      // Reject replayed TOTP codes
+      const replayCheck = await prisma.$transaction(async (tx) => {
+        const rows = await tx.$queryRaw<
+          Array<{ totp_last_used_counter: number | null }>
+        >`SELECT totp_last_used_counter FROM users WHERE id = ${user.id} FOR UPDATE`;
+        const lastCounter = rows[0]?.totp_last_used_counter ?? null;
+        if (
+          lastCounter !== null &&
+          verifyResult.counter !== null &&
+          verifyResult.counter <= lastCounter
+        ) {
+          return { replay: true };
+        }
+        await tx.$executeRaw`UPDATE users SET totp_last_used_counter = ${verifyResult.counter} WHERE id = ${user.id}`;
+        return { replay: false };
+      });
+
+      if (replayCheck.replay) {
+        return error(reply, "TOTP kód již byl použit", 401);
+      }
+
       // Reset failed attempts and update last login (TOTP verified = successful login)
       await prisma.users.update({
         where: { id: user.id },