security: fix all Critical and High findings from FLAWS_REPORT audit

- Auth: pessimistic locking on login tokens and refresh token rotation,
  backup code attempt counter, rate limiting verification
- Schema: unique constraints on business numbers, FK relations,
  unsigned/signed alignment, attendance duplicate prevention
- Invoices/PDFs: DOMPurify sanitization, bounded queries in stats
  and alerts, VAT rounding, Puppeteer error handling
- Orders/Offers: transactional parent+child creation, Zod NaN
  refinement, status enums, uniqueness checks
- Projects/Files: path traversal protection, streamed uploads,
  permission guards, query param validation
- Attendance/HR: duplicate checks, ownership validation, GPS
  restrictions, trip distance validation
- Frontend: modal lock reference counting, XSS escaping in print
  HTML, ref mutation fixes, accessibility attributes

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

src/routes/admin/trips.ts

@@ -206,6 +206,10 @@ export default async function tripsRoutes(
     const body = parsed.data;
     const authData = request.authData!;
 
+    if (body.end_km < body.start_km) {
+      return error(reply, "Konečný stav km nesmí být menší než počáteční", 400);
+    }
+
     const trip = await prisma.trips.create({
       data: {
         vehicle_id: Number(body.vehicle_id),
@@ -247,6 +251,18 @@ export default async function tripsRoutes(
       const body = parsed.data;
       const authData = request.authData!;
 
+      if (
+        body.end_km != null &&
+        body.start_km != null &&
+        body.end_km < body.start_km
+      ) {
+        return error(
+          reply,
+          "Konečný stav km nesmí být menší než počáteční",
+          400,
+        );
+      }
+
       const existing = await prisma.trips.findUnique({ where: { id } });
       if (!existing) return error(reply, "Jízda nenalezena", 404);