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/SaleResource.php

@@ -54,7 +54,7 @@ class SaleResource extends Resource
                     ->live(),
                 TextInput::make('current_series')
                     ->label('Series')
-                    ->disabled(),
+                    ->readOnly(),
                 DatePicker::make('happened_on')->label('Date')
                     ->required()
                     ->afterStateUpdated(function ($set, $get) {
@@ -220,17 +220,10 @@ class SaleResource extends Resource
     {
         return $table
             ->columns([
-                TextColumn::make('id')->label('ID')->sortable(),
-                TextColumn::make('client.name')->label('Client')->sortable(),
-                TextColumn::make('branch.name')->label('Branch')->sortable(),
+                TextColumn::make('branch.code')->label('Branch')->sortable(),
+                TextColumn::make('reference_number')->label('Reference Number')->sortable(),
                 TextColumn::make('happened_on')->label('Date')->date()->sortable(),
-                TextColumn::make('gross_amount')->label('Gross Amount')->numeric()->sortable(),
-                TextColumn::make('exempt')->label('Exempt')->numeric()->sortable(),
-                TextColumn::make('vatable_amount')->label('Vatable Amount')->numeric()->sortable(),
-                TextColumn::make('output_tax')->label('Output Tax')->numeric()->sortable(),
-                TextColumn::make('payable_withholding_tax')->label('Payable Withholding Tax')->numeric()->sortable(),
-                TextColumn::make('discount')->label('Discount')->numeric()->sortable(),
-                TextColumn::make('net_amount')->label('Net Amount')->numeric()->sortable(),
+                TextColumn::make('user.name')->label('Created By')->sortable(),
             ])
             ->filters([
                 //