Auto-deduct spice inventory when batch is created/updated/deleted

- Add size_id, units_produced, quantity_g to batches table
- quantity_g auto-calculated from units × packing size on save
- Batch model deducts spice quantities on create, reverses on delete,
  recalculates on update when relevant fields change
- Batch form shows live total weight preview
- Chargen table shows units + grams produced

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Filament/User/Resources/BatchResource.php

@@ -4,11 +4,13 @@ namespace App\Filament\User\Resources;
 
 use App\Filament\User\Resources\BatchResource\Pages;
 use App\Models\Batch;
+use App\Models\ProductSize;
 use App\Models\Recipe;
 use Filament\Forms;
 use Filament\Forms\Form;
 use Filament\Forms\Get;
 use Filament\Resources\Resource;
+use Illuminate\Support\HtmlString;
 use Filament\Tables;
 use Filament\Tables\Table;
 
@@ -38,6 +40,17 @@ class BatchResource extends Resource
                     ->searchable()
                     ->preload()
                     ->required()
+                    ->live()
+                    ->afterStateUpdated(fn ($set) => $set('size_id', null)),
+
+                Forms\Components\Select::make('size_id')
+                    ->label('Variante (Verpackung)')
+                    ->options(fn (Get $get) => ProductSize::with('packing')
+                        ->where('product_id', $get('product_id'))
+                        ->get()
+                        ->mapWithKeys(fn ($s) => [$s->id => $s->packing->name . ' ' . $s->packing->size . 'g'])
+                    )
+                    ->required()
                     ->live(),
 
                 Forms\Components\Select::make('recipe_id')
@@ -48,6 +61,25 @@ class BatchResource extends Resource
                     ->required()
                     ->live(),
 
+                Forms\Components\TextInput::make('units_produced')
+                    ->label('Anzahl Einheiten')
+                    ->numeric()
+                    ->required()
+                    ->live(debounce: 400),
+
+                Forms\Components\Placeholder::make('quantity_g_preview')
+                    ->label('Gesamtgewicht (berechnet)')
+                    ->content(function (Get $get): HtmlString {
+                        $units = (int) $get('units_produced');
+                        $sizeId = $get('size_id');
+                        if (! $units || ! $sizeId) {
+                            return new HtmlString('<span class="text-gray-400">—</span>');
+                        }
+                        $size = ProductSize::with('packing')->find($sizeId);
+                        $totalG = $units * ($size?->packing?->size ?? 0);
+                        return new HtmlString("<strong>{$totalG} g</strong> ({$units} × {$size?->packing?->size}g)");
+                    }),
+
                 Forms\Components\DatePicker::make('produced_at')
                     ->label('Produktionsdatum'),