feat: add account linking and improve sales table

- Add many-to-many relationships between Sale/Expense and Account models
- Create pivot tables for account_sale and account_expense with migrations
- Implement account syncing during sale/expense creation and editing
- Add accounts_list attribute to display comma-separated account names
- Introduce SaleService with DTO for sale creation logic
- Simplify sales table columns to show branch, reference, date, and creator
- Calculate and store aggregated financial fields from transactions
- Make series field read-only instead of disabled in sale form

app/Services/Sales/SaleService.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Services\Sales;
+
+use App\DataObjects\CreateSaleDTO;
+use App\Models\Sale;
+use Carbon\Carbon;
+use Illuminate\Support\Facades\Auth;
+
+class SaleService
+{
+    /**
+     * Create a new class instance.
+     */
+    public function __construct()
+    {
+        //
+    }
+
+    public function create(array $data): Sale
+    {
+        
+        $tData = new CreateSaleDTO(
+            reference_number: $data['current_series'], 
+            happened_on: Carbon::parse($data['happened_on']),
+            branch_id: $data['branch_id'],
+            user_id: Auth::user()->id,
+        );
+        return Sale::create($tData->toArray());
+    }
+}