feat: add discount management and PDF export for transmittals

- Create Discount model, migration, and Filament resource with relation to Client
- Add PDF export functionality for transmittals using DomPDF
- Include discount type selection in sales transactions
- Fix account filtering logic in expense resource
- Update export job to generate PDF instead of Excel

app/Filament/Resources/SaleResource.php

@@ -6,6 +6,7 @@ use App\Filament\Resources\SaleResource\Pages;
 use App\Models\Account;
 use App\Models\Branch;
 use App\Models\Client;
+use App\Models\Discount;
 use App\Models\Sale;
 use Awcodes\TableRepeater\Components\TableRepeater;
 use Awcodes\TableRepeater\Header;
@@ -30,17 +31,17 @@ class SaleResource extends Resource
 
     protected static bool $shouldRegisterNavigation = false;
 
+    
     public static function form(Form $form): Form
     {
         return $form
             ->schema([
                 Select::make('client')
-                    ->default(request()->query('client_id'))
+                    ->default(fn () => request()->integer('client_id'))
                     ->options(Client::query()->get()->pluck('company', 'id'))
                     ->afterStateUpdated(function ($set, $get) {
                         $set('branch_id', '');
                     })
-                    ->disabled()
                     ->required()
                     ->live(),
                 Select::make('branch_id')
@@ -72,6 +73,8 @@ class SaleResource extends Resource
             ]);
     }
 
+    
+
     public static function getSeries(Get $get): string
     {
         $branch = Branch::find($get('branch_id'));
@@ -98,6 +101,7 @@ class SaleResource extends Resource
                 Header::make('Output Tax'),
                 Header::make('Withholding Tax'),
                 Header::make('Discount'),
+                Header::make('Discount Type'),
                 Header::make('Net Amount'),
             ];
         }
@@ -136,7 +140,7 @@ class SaleResource extends Resource
                 ->numeric()
                 ->nullable()
                 ->live()
-                ->readOnly()
+                ->readOnly(fn (Get $get) => $get('exempt') == 0)
                 ->default(0),
             Hidden::make('happened_on')->default(fn (Get $get) => $get('../../happened_on')),
             Hidden::make('with_discount')->default(fn (Get $get) => $get('../../with_discount')),
@@ -159,6 +163,9 @@ class SaleResource extends Resource
                 ->readOnly()
                 ->visible(fn (Get $get) => $get('../../with_discount'))
                 ->live(),
+            Select::make('discount_type')
+                ->options(fn (Get $get) => static::getDiscountOptions($get))
+                ->visible(fn (Get $get) => $get('../../with_discount')),
             TextInput::make('net_amount')->numeric()->default(0),
         ];
     }
@@ -184,6 +191,13 @@ class SaleResource extends Resource
         return $query->get()->pluck('account', 'id');
     }
 
+    private static function getDiscountOptions(Get $get)
+    {
+        $query = Discount::query()->where('client_id', $get('../../client'));
+ 
+        return $query->pluck('discount', 'id');
+    }
+
     private static function setDefaultFormValues(Get $get, Set $set, ?string $old, ?string $state)
     {
         $exempt = (float) $get('exempt');