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/services/drawer.service.ts

@@ -19,6 +19,7 @@ export const DrawerService = {
       .insert(drawerSessions)
       .values({
         locationId: input.locationId,
+        registerId: input.registerId,
         openedBy,
         openingBalance: input.openingBalance.toString(),
       })