- Add 'Corte Z' button in secondary actions panel
- Add modal showing register summary before closing:
- opening amount, total sales, cash sales, change given
- cash movements in/out, cancellations, expected cash
- payment method breakdown and movement detail list
- loadCutX() fetches current register summary (read-only)
- confirmCutZ() calls POST /pos/api/register/cut-z with counted amount
- Auto-fills closing amount with expected cash
- Shows toast with difference after closing
- Resets register state to 'Sin caja abierta' after close
- Bump pos.css and pos.js cache-bust to v=3