feat: Phase 2E — cash drawer reconciliation

Backend:
- WaiterShift: add counted_cash_end (physical cash handed over) + cash_discrepancy (computed)
- BusinessDay: add store_opening_cash, store_closing_cash, store_cash_discrepancy
- EndShiftRequest: accept counted_cash_end (optional)
- CloseBusinessDayRequest: accept store_closing_cash (optional)
- Shift end (both /end and /manager/end/{id}): compute cash_discrepancy =
  counted_cash_end - (starting_cash + total_collected); negative = short, positive = over
- Business day close: compute store_cash_discrepancy = store_closing_cash - expected;
  expected = store_opening_cash + sum(shift.total_collected for day)
- _enrich_shift: expose counted_cash_end + cash_discrepancy in all shift responses
- Business day summary: expose store cash fields + store_expected_closing + total_waiter_collected
- BusinessDayOut schema: expose new store cash fields
- Shifts CSV export: add counted_cash_end + cash_discrepancy columns

Frontend:
- EndShiftConfirmModal: 2-step flow — step 1 notes, step 2 cash handover with live discrepancy
  (shows ✓ clean / ⚠ short / ⚠ over in real time before confirming)
- WorkdaySummaryModal close flow: new Ταμείο tab with store cash count + live discrepancy;
  footer navigates overview → Ταμείο → Έλεγχοι; store_closing_cash included in close payload
- ShiftsOverview report: Ταμείο column showing counted_cash_end + discrepancy badge
- ShiftDetailModal row 2: replaces Εξ.Τραπεζιών with Παραδόθηκαν + Ταμείο discrepancy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

local_backend/routers/shifts.py

@@ -90,6 +90,9 @@ def _enrich_shift(shift: WaiterShift, db: Session) -> dict:
         "hourly_rate_snapshot": shift.hourly_rate_snapshot,
         "duration_hours": pay_data["duration_hours"],
         "shift_pay": pay_data["shift_pay"],
+        # Phase 2E
+        "counted_cash_end": shift.counted_cash_end,
+        "cash_discrepancy": shift.cash_discrepancy,
         "breaks": [
             {"id": b.id, "shift_id": b.shift_id, "started_at": _dt(b.started_at), "ended_at": _dt(b.ended_at)}
             for b in shift.breaks
@@ -166,10 +169,16 @@ def end_shift(
         raise HTTPException(status_code=404, detail="No active shift found")
 
     now = datetime.now(timezone.utc)
-    shift.total_collected = compute_shift_total(shift.id, db)
+    total = compute_shift_total(shift.id, db)
+    shift.total_collected = total
     shift.ended_at = now
     if body.notes:
         shift.notes = body.notes
+    # Phase 2E: cash reconciliation
+    if body.counted_cash_end is not None:
+        shift.counted_cash_end = body.counted_cash_end
+        expected = (shift.starting_cash or 0.0) + total
+        shift.cash_discrepancy = round(body.counted_cash_end - expected, 2)
 
     open_break = db.query(ShiftBreak).filter(
         ShiftBreak.shift_id == shift.id, ShiftBreak.ended_at == None
@@ -233,10 +242,16 @@ def manager_end_shift(
         raise HTTPException(status_code=404, detail="Active shift not found")
 
     now = datetime.now(timezone.utc)
-    shift.total_collected = compute_shift_total(shift.id, db)
+    total = compute_shift_total(shift.id, db)
+    shift.total_collected = total
     shift.ended_at = now
     if body.notes:
         shift.notes = body.notes
+    # Phase 2E: cash reconciliation
+    if body.counted_cash_end is not None:
+        shift.counted_cash_end = body.counted_cash_end
+        expected = (shift.starting_cash or 0.0) + total
+        shift.cash_discrepancy = round(body.counted_cash_end - expected, 2)
 
     open_break = db.query(ShiftBreak).filter(
         ShiftBreak.shift_id == shift.id, ShiftBreak.ended_at == None