feat(shift): cash drawer balance carried across shifts + admin cash movements

New signed cash_movement event (admin-only): load/remove drawer float, signed +
attributed. ShiftService folds cash payments + movements by time into a drawer
balance; shift open auto-inherits the prior shift's expected closing drawer as its
opening float; the Z-report reports opening/taken/added/removed/expected (= next
shift's opening float). Card payments excluded (settle to bank). Routes: POST
/api/cash-movement, drawer in GET /api/shift/current. ShiftControl shows the live
drawer + admin load/remove form + Z-report drawer block. Wiki: shift.md.

packages/shared/src/index.ts

@@ -52,6 +52,10 @@ export type LedgerEventType =
   // with a takings summary (shift_z_report). See wiki/concepts/shift.md.
   | "shift_open"
   | "shift_z_report"
+  // Admin loads/removes physical drawer cash (the float). Signed payload:
+  // { amountMinor (signed: + load, − removal), reason, currency, operator }.
+  // Folds into the drawer balance carried across shifts. See wiki/concepts/shift.md.
+  | "cash_movement"
   | "anomaly";
 
 /** How money was tendered (for payment events + the shift Z-report). */