fix: require open drawer to complete transactions, fix product price field

- Backend enforces open drawer at location before completing any transaction
- Frontend disables payment buttons when drawer is closed with warning message
- Fix product price field name (price, not sellingPrice) in POS API types
- Fix seed UUIDs to use valid UUID v4 format (version nibble must be 1-8)
- Fix Vite allowedHosts for dev.lunarfront.tech access
- Add e2e test for drawer enforcement (39 POS tests now pass)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/backend/src/services/transaction.service.ts

@@ -5,6 +5,7 @@ import {
   transactionLineItems,
   discountAudits,
   discounts,
+  drawerSessions,
 } from '../db/schema/pos.js'
 import { products, inventoryUnits } from '../db/schema/inventory.js'
 import { companies, locations } from '../db/schema/stores.js'
@@ -231,6 +232,18 @@ export const TransactionService = {
     if (!txn) throw new NotFoundError('Transaction')
     if (txn.status !== 'pending') throw new ConflictError('Transaction is not pending')
 
+    // Require an open drawer session at the transaction's location
+    if (txn.locationId) {
+      const [openDrawer] = await db
+        .select({ id: drawerSessions.id })
+        .from(drawerSessions)
+        .where(and(eq(drawerSessions.locationId, txn.locationId), eq(drawerSessions.status, 'open')))
+        .limit(1)
+      if (!openDrawer) {
+        throw new ValidationError('Cannot complete transaction without an open drawer at this location')
+      }
+    }
+
     // Validate cash payment (with optional nickel rounding)
     let changeGiven: string | undefined
     let roundingAdjustment = 0