feat: named registers, X/Z reports, daily rollup, fix drawerSessionId

Registers:
- New register table with location association
- CRUD service + API routes (POST/GET/PATCH/DELETE /registers)
- Drawer sessions now link to a register via registerId
- Register ID persisted in localStorage per device

X/Z Reports:
- ReportService with getDrawerReport() (X or Z depending on session state)
- Z report auto-displayed on drawer close in the drawer dialog
- X report (Current Shift Report) button on open drawer view
- Report shows: sales summary, payment breakdown, discounts, cash accountability, adjustments

Daily Rollup:
- ReportService.getDailyReport() aggregates all sessions at a location for a date
- New /reports/daily endpoint with locationId + date params
- Frontend daily report page with date picker, location selector, session breakdown

Critical Fix:
- drawerSessionId is now populated on transactions when completing (was never set before)
- This enables accurate per-drawer reporting and cash accountability

Migration 0044: register table, drawer_session.register_id column

Tests: 14 new (register CRUD, drawer report X/Z, drawerSessionId population, daily rollup, register-drawer link)
Full suite: 367 passed

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

packages/backend/src/db/schema/pos.ts

@@ -70,9 +70,21 @@ export const discounts = pgTable('discount', {
 
 export const adjustmentTypeEnum = pgEnum('adjustment_type', ['cash_in', 'cash_out'])
 
+export const registers = pgTable('register', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  locationId: uuid('location_id')
+    .notNull()
+    .references(() => locations.id),
+  name: varchar('name', { length: 100 }).notNull(),
+  isActive: boolean('is_active').notNull().default(true),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+})
+
 export const drawerSessions = pgTable('drawer_session', {
   id: uuid('id').primaryKey().defaultRandom(),
   locationId: uuid('location_id').references(() => locations.id),
+  registerId: uuid('register_id').references(() => registers.id),
   openedBy: uuid('opened_by')
     .notNull()
     .references(() => users.id),