feat(phase-12/13/14): jobs, mail notifications, and PDF views (in-progress)

Phase 12 - Queue & Background Jobs:
- SendInvoiceNotificationJob, ProcessLowStockAlertJob,
  GeneratePayslipJob, ProcessBulkImportJob
- Dispatch jobs from low-stock and payroll listeners
- InvoiceApiController dispatches SendInvoiceNotificationJob on store

Phase 13 - Email Notifications:
- InvoiceCreatedMail, LowStockAlertMail, PayrollApprovedMail,
  ApprovalRequestMail Mailables
- Blade email templates for all 4 notification types
- Listeners dispatch queued mail alongside existing side-effects

Phase 14 - PDF Generation (views only, controller pending):
- resources/views/pdfs/invoice.blade.php
- resources/views/pdfs/purchase-order.blade.php
- resources/views/pdfs/payslip.blade.php

Co-Authored-By: Claude <noreply@anthropic.com>

Author: claude

composer.json

@@ -0,0 +1,6 @@
+{
+  "require": {
+    "barryvdh/laravel-dompdf": "^3.1",
+    "maatwebsite/excel": "^3.1"
+  }
+}