Add piece_weight calibration: enter Stück + Gramm per delivery, average auto-calculated

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

database/migrations/2026_09_13_000000_add_piece_weight_to_spices_and_suppliers.php

@@ -0,0 +1,30 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('spices', function (Blueprint $table) {
+            $table->decimal('piece_weight', 10, 3)->nullable()->after('unit');
+        });
+
+        Schema::table('spices_suppliers', function (Blueprint $table) {
+            $table->decimal('weight_g', 10, 3)->nullable()->after('amount');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('spices', function (Blueprint $table) {
+            $table->dropColumn('piece_weight');
+        });
+
+        Schema::table('spices_suppliers', function (Blueprint $table) {
+            $table->dropColumn('weight_g');
+        });
+    }
+};