feat: add drawer cash in/out adjustments with balance reconciliation

- New drawer_adjustment table (type: cash_in/cash_out, amount, reason)
- POST/GET /drawer/:id/adjustments endpoints
- Drawer close calculation now includes adjustments: expected = opening + sales + cash_in - cash_out
- DrawerAdjustmentSchema for input validation
- 5 new tests (44 total POS tests passing)

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

packages/shared/src/schemas/index.ts

@@ -180,6 +180,7 @@ export {
   DiscountUpdateSchema,
   DrawerOpenSchema,
   DrawerCloseSchema,
+  DrawerAdjustmentSchema,
 } from './pos.schema.js'
 export type {
   TransactionCreateInput,
@@ -190,6 +191,7 @@ export type {
   DiscountUpdateInput,
   DrawerOpenInput,
   DrawerCloseInput,
+  DrawerAdjustmentInput,
 } from './pos.schema.js'
 
 export { LogLevel, AppConfigUpdateSchema } from './config.schema.js'

packages/shared/src/schemas/pos.schema.ts

@@ -104,6 +104,13 @@ export const DrawerOpenSchema = z.object({
 })
 export type DrawerOpenInput = z.infer<typeof DrawerOpenSchema>
 
+export const DrawerAdjustmentSchema = z.object({
+  type: z.enum(['cash_in', 'cash_out']),
+  amount: z.coerce.number().min(0.01),
+  reason: z.string().min(1),
+})
+export type DrawerAdjustmentInput = z.infer<typeof DrawerAdjustmentSchema>
+
 export const DrawerCloseSchema = z.object({
   closingBalance: z.coerce.number().min(0),
   denominations: z