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/DiscountResource.php

@@ -0,0 +1,73 @@
+<?php
+
+namespace App\Filament\Resources;
+
+use App\Filament\Resources\DiscountResource\Pages;
+use App\Filament\Resources\DiscountResource\RelationManagers;
+use App\Models\Discount;
+use Filament\Forms;
+use Filament\Forms\Form;
+use Filament\Forms\Get;
+use Filament\Resources\Resource;
+use Filament\Tables;
+use Filament\Tables\Table;
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\SoftDeletingScope;
+
+class DiscountResource extends Resource
+{
+    protected static ?string $model = Discount::class;
+
+    protected static ?string $navigationIcon = 'heroicon-o-rectangle-stack';
+
+    protected static bool $shouldRegisterNavigation = false;
+
+    public static function form(Form $form): Form
+    {
+        return $form
+            ->schema([
+                Forms\Components\TextInput::make('discount')
+                    ->label('Discount')
+                    ->required(),
+                Forms\Components\Hidden::make('client_id')
+                    ->default(fn () => request()->client_id),
+            ]);
+    }
+
+    public static function table(Table $table): Table
+    {
+        return $table
+            ->columns([
+                Tables\Columns\TextColumn::make('discount')
+                    ->label('Discount')
+                    ->searchable(),
+            ])
+            ->filters([
+                //  
+            ])
+            ->actions([
+                Tables\Actions\EditAction::make(),
+            ])
+            ->bulkActions([
+                Tables\Actions\BulkActionGroup::make([
+                    Tables\Actions\DeleteBulkAction::make(),
+                ]),
+            ]);
+    }
+
+    public static function getRelations(): array
+    {
+        return [
+            //
+        ];
+    }
+
+    public static function getPages(): array
+    {
+        return [
+            'index' => Pages\ListDiscounts::route('/'),
+            'create' => Pages\CreateDiscount::route('/create'),
+            'edit' => Pages\EditDiscount::route('/{record}/edit'),
+        ];
+    }
+}