Add formula-based product pricing (P/W/MG) for Parsian-style unit prices.

Port FormulaPriceService from colleague app so admins can compute a single unit price from reference mid, weight, and wage instead of offset coefficients.

Co-authored-by: Cursor <cursoragent@cursor.com>

database/migrations/2026_08_10_000001_add_price_formula_fields_to_products_table.php

@@ -0,0 +1,48 @@
+<?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
+    {
+        if (! Schema::hasTable('products')) {
+            return;
+        }
+
+        Schema::table('products', function (Blueprint $table) {
+            if (! Schema::hasColumn('products', 'price_formula_enabled')) {
+                if (Schema::hasColumn('products', 'app_price')) {
+                    $table->boolean('price_formula_enabled')->default(false)->after('app_price');
+                } else {
+                    $table->boolean('price_formula_enabled')->default(false);
+                }
+            }
+            if (! Schema::hasColumn('products', 'price_formula')) {
+                $table->text('price_formula')->nullable()->after('price_formula_enabled');
+            }
+        });
+    }
+
+    public function down(): void
+    {
+        if (! Schema::hasTable('products')) {
+            return;
+        }
+
+        Schema::table('products', function (Blueprint $table) {
+            $drop = [];
+            if (Schema::hasColumn('products', 'price_formula_enabled')) {
+                $drop[] = 'price_formula_enabled';
+            }
+            if (Schema::hasColumn('products', 'price_formula')) {
+                $drop[] = 'price_formula';
+            }
+            if ($drop !== []) {
+                $table->dropColumn($drop);
+            }
+        });
+    }
+};