Introduce spice_stock_movements ledger for traceable stock changes

Every delivery and batch now writes a signed movement entry instead of
directly incrementing/decrementing spice.quantity. The balance is always
the sum of all movements. Existing data is backfilled in the migration.
Rohstoff edit page shows the full movement history (Lagerbewegungen tab).

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

app/Filament/User/Resources/SpiceSupplierResource/Pages/CreateSpiceSupplier.php

@@ -4,17 +4,8 @@ namespace App\Filament\User\Resources\SpiceSupplierResource\Pages;
 
 use App\Filament\User\Resources\SpiceSupplierResource;
 use Filament\Resources\Pages\CreateRecord;
-use Illuminate\Database\Eloquent\Model;
-use App\Models\Spice;
 
 class CreateSpiceSupplier extends CreateRecord
 {
     protected static string $resource = SpiceSupplierResource::class;
-
-    protected function handleRecordCreation(array $data): Model {
-        $record = static::getModel()::create($data);
-
-        Spice::findOrFail($data['spice_id'])->increment('quantity', $data['amount']);
-        return $record;
-    }
 }