Add profit analysis modal and cost tracking for products

Introduces a Profit Analysis modal for products, allowing users to view profit, margin, and markup calculations based on cost per unit and pricing tiers. Adds cost per unit input to the product modal, updates product types, and integrates the analysis modal into the products page and product table. This enhances product management with profit tracking and analysis features.

lib/types/index.ts

@@ -47,6 +47,7 @@ export interface Product {
   enabled?: boolean
   pricing: PricingTier[]
   image?: string | File | null
+  costPerUnit?: number // Cost price for profit calculations
 }
 
 export interface ProductData extends Product {}