feat(server): evaluate price alerts per product and fix gold discharge rounding

Alerts now bind to a product_id and share one evaluator; displayed gold within a rounding step discharges the full wallet.

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

app/Models/PriceTrigger.php

@@ -9,8 +9,11 @@ class PriceTrigger extends Model
 {
     use HasFactory, SoftDeletes;
 
+    private static ?bool $productIdColumnExists = null;
+
     protected $fillable = [
         'customer_id',
+        'product_id',
         'target_price',
         'price_condition',
         'action',
@@ -20,8 +23,32 @@ class PriceTrigger extends Model
     protected $casts = [
         "is_active" => "boolean",
     ];
+
+    public static function hasProductIdColumn(): bool
+    {
+        if (static::$productIdColumnExists !== null) {
+            return static::$productIdColumnExists;
+        }
+
+        try {
+            static::$productIdColumnExists = \Illuminate\Support\Facades\Schema::hasColumn(
+                (new static)->getTable(),
+                'product_id'
+            );
+        } catch (\Throwable) {
+            static::$productIdColumnExists = false;
+        }
+
+        return static::$productIdColumnExists;
+    }
+
     public function customer()
     {
         return $this->belongsTo(Customer::class);
     }
+
+    public function product()
+    {
+        return $this->belongsTo(Product::class);
+    }
 }