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/Models/Expense.php

@@ -5,6 +5,7 @@ namespace App\Models;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\MorphMany;
 
 class Expense extends Model
@@ -43,4 +44,14 @@ class Expense extends Model
     {
         return $this->belongsTo(Branch::class);
     }
+
+    public function accounts(): BelongsToMany
+    {
+        return $this->belongsToMany(Account::class, 'account_expense')->withTimestamps();
+    }
+
+    public function getAccountsListAttribute(): string
+    {
+        return $this->accounts->pluck('account')->implode(', ');
+    }
 }

app/Models/Sale.php

@@ -5,6 +5,7 @@ namespace App\Models;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Illuminate\Database\Eloquent\Relations\MorphMany;
 
 class Sale extends Model
@@ -43,4 +44,19 @@ class Sale extends Model
     {
         return $this->belongsTo(Branch::class);
     }
+
+    public function accounts(): BelongsToMany
+    {
+        return $this->belongsToMany(Account::class, 'account_sale')->withTimestamps();
+    }
+
+    public function getAccountsListAttribute(): string
+    {
+        return $this->accounts->pluck('account')->implode(', ');
+    }
+
+    public function user(): BelongsTo
+    {
+        return $this->belongsTo(User::class);
+    }
 }