feat(admin): let price alerts pick a product

Show the product on the form and table so each alert is tied to one item.

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

src/model/priceTriggers.ts

@@ -1,6 +1,8 @@
 export interface PriceTriggers{
     id?: number
     customer_id: number
+    product_id?: number
+    product?: { id: number; title?: string }
     target_price: number
     price_condition: string
     action: string