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/Filament/Resources/ExpenseResource/Pages/CreateExpense.php

@@ -58,6 +58,16 @@ class CreateExpense extends CreateRecord
 
     public function getFormDataMutation(array $data): array
     {
+        $transactions = $data['transactions'] ?? [];
+
+        $data['gross_amount'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['gross_amount'] ?? 0));
+        $data['exempt'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['exempt'] ?? 0));
+        $data['zero_rated'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['zero_rated'] ?? 0));
+        $data['vatable_amount'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['vatable_amount'] ?? 0));
+        $data['input_tax'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['input_tax'] ?? 0));
+        $data['payable_withholding_tax'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['payable_withholding_tax'] ?? 0));
+        $data['net_amount'] = collect($transactions)->sum(fn (array $transaction) => (float) ($transaction['net_amount'] ?? 0));
+
         return Arr::except($data, ['client', 'transactions']);
     }
 
@@ -85,6 +95,15 @@ class CreateExpense extends CreateRecord
                 )->thenReturn();
             }
 
+            $accountIds = collect($transactions)
+                ->pluck('account_id')
+                ->filter()
+                ->unique()
+                ->values()
+                ->all();
+
+            $this->getRecord()->accounts()->sync($accountIds);
+
             $this->commitDatabaseTransaction();
         } catch (Exception $exception) {
             $this->rollBackDatabaseTransaction();