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/business_day.py

@@ -150,6 +150,15 @@ def close_business_day(
     if body.notes:
         day.notes = body.notes
 
+    # Phase 2E: store-level cash reconciliation
+    if body.store_closing_cash is not None:
+        day.store_closing_cash = body.store_closing_cash
+        # expected = store_opening_cash + sum of all waiter collected amounts this day
+        all_shifts = db.query(WaiterShift).filter(WaiterShift.business_day_id == day.id).all()
+        total_collected = sum(s.total_collected or 0.0 for s in all_shifts)
+        expected_closing = (day.store_opening_cash or 0.0) + total_collected
+        day.store_cash_discrepancy = round(body.store_closing_cash - expected_closing, 2)
+
     db.commit()
     db.refresh(day)
 
@@ -409,6 +418,10 @@ def business_day_summary(
         for key in ("total_collected", "total_items_value", "cash", "card", "transfer", "treat", "other"):
             w[key] = round(w[key], 2)
 
+    # Phase 2E: store-level cash totals for summary view
+    total_waiter_collected = sum(s.total_collected or 0.0 for s in shifts)
+    store_expected_closing = (day.store_opening_cash or 0.0) + total_waiter_collected
+
     return {
         "day_id": day.id,
         "status": day.status,
@@ -425,6 +438,12 @@ def business_day_summary(
             "with_unpaid_items": with_unpaid_items,
             "active_shifts": active_shift_count,
         },
+        # Phase 2E
+        "store_opening_cash": day.store_opening_cash,
+        "store_closing_cash": day.store_closing_cash,
+        "store_cash_discrepancy": day.store_cash_discrepancy,
+        "store_expected_closing": round(store_expected_closing, 2),
+        "total_waiter_collected": round(total_waiter_collected, 2),
     }