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/migrations/0044_registers-reports.sql

@@ -0,0 +1,12 @@
+-- Named registers for POS terminals
+CREATE TABLE IF NOT EXISTS register (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  location_id UUID NOT NULL REFERENCES location(id),
+  name VARCHAR(100) NOT NULL,
+  is_active BOOLEAN NOT NULL DEFAULT true,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Link drawer sessions to registers
+ALTER TABLE drawer_session ADD COLUMN IF NOT EXISTS register_id UUID REFERENCES register(id);

packages/backend/src/db/migrations/meta/_journal.json

@@ -316,6 +316,13 @@
       "when": 1775680000000,
       "tag": "0043_repair-pos-consumable",
       "breakpoints": true
+    },
+    {
+      "idx": 44,
+      "version": "7",
+      "when": 1775770000000,
+      "tag": "0044_registers-reports",
+      "breakpoints": true
     }
   ]
 }