feat: consolidate Stall types and create reusable CartButton component

## Type Consolidation
- Add StallApiResponse interface matching LNbits backend structure
- Update domain Stall interface with cleaner, app-friendly properties
- Create mapApiResponseToStall() mapper function for API-to-domain conversion
- Remove duplicate Stall type definition from nostrmarketAPI.ts
- Update CheckoutPage to use standardized shipping property
- Verify types against LNbits reference implementation

## UI Components
- Create reusable CartButton.vue component with proper separation of concerns
- Remove duplicate cart button code from MarketPage and StallView
- Add consistent cart functionality across all market pages
- Fix missing cart button in StallView
- Improve code maintainability with DRY principles

## Bug Fixes
- Fix ProductDetailDialog add-to-cart functionality by using correct cart system
- Resolve cart system mismatch between legacy addToCart and stall-based totalCartItems
- Update ProductCard to emit events properly instead of direct store call
- Ensure consistent event flow: ProductCard → ProductGrid → MarketPage → Store

## Technical Improvements
- Follow established Product type consolidation pattern for consistency
- Maintain type safety between API responses and domain models
- Enable easier API evolution without breaking domain logic
- Optimize bundle splitting with component extraction

src/modules/market/services/nostrmarketAPI.ts

@@ -17,25 +17,11 @@ export interface Merchant {
   }
 }
 
-export interface Stall {
-  id: string
-  wallet: string
-  name: string
-  currency: string
-  shipping_zones: Array<{
-    id: string
-    name: string
-    cost: number
-    countries: string[]
-  }>
-  config: {
-    image_url?: string
-    description?: string
-  }
-  pending: boolean
-  event_id?: string
-  event_created_at?: number
-}
+// Import StallApiResponse from types/market.ts
+import type { StallApiResponse } from '../types/market'
+
+// Use StallApiResponse as the API response type
+export type Stall = StallApiResponse
 
 export interface CreateMerchantRequest {
   config: {

src/modules/market/types/market.ts

@@ -13,6 +13,7 @@ export interface Market {
   }
 }
 
+// Domain Model - Single source of truth for Stall
 export interface Stall {
   id: string
   pubkey: string
@@ -20,8 +21,7 @@ export interface Stall {
   description?: string
   logo?: string
   categories?: string[]
-  shipping?: ShippingZone[]
-  shipping_zones?: ShippingZone[]  // LNbits format
+  shipping: ShippingZone[]
   currency: string
   nostrEventId?: string
 }
@@ -48,7 +48,7 @@ export interface Product {
 }
 
 // Type aliases for API responses - imported from services
-export type { ProductApiResponse, Stall as StallApiResponse } from '../services/nostrmarketAPI'
+export type { ProductApiResponse } from '../services/nostrmarketAPI'
 
 // Mapping function to convert API response to domain model
 export function mapApiResponseToProduct(
@@ -76,17 +76,19 @@ export function mapApiResponseToProduct(
   }
 }
 
-// Mapping function to convert API response to domain model for Stall
+// Mapper function to convert API response to domain model
 export function mapApiResponseToStall(
-  apiStall: import('../services/nostrmarketAPI').Stall
+  apiStall: StallApiResponse,
+  pubkey: string = '',
+  categories: string[] = []
 ): Stall {
   return {
     id: apiStall.id,
-    pubkey: '', // API Stall doesn't have pubkey, need to set from merchant context
+    pubkey,
     name: apiStall.name,
     description: apiStall.config?.description,
     logo: apiStall.config?.image_url,
-    categories: [], // API Stall doesn't have categories
+    categories,
     shipping: apiStall.shipping_zones?.map(zone => ({
       id: zone.id,
       name: zone.name,
@@ -96,17 +98,7 @@ export function mapApiResponseToStall(
       description: `${zone.name} shipping`,
       estimatedDays: undefined,
       requiresPhysicalShipping: true
-    })),
-    shipping_zones: apiStall.shipping_zones?.map(zone => ({
-      id: zone.id,
-      name: zone.name,
-      cost: zone.cost,
-      currency: apiStall.currency,
-      countries: zone.countries,
-      description: `${zone.name} shipping`,
-      estimatedDays: undefined,
-      requiresPhysicalShipping: true
-    })),
+    })) || [],
     currency: apiStall.currency,
     nostrEventId: apiStall.event_id
   }
@@ -173,6 +165,27 @@ export interface ShippingZone {
   requiresPhysicalShipping?: boolean
 }
 
+// API Response Types - Raw data from LNbits backend
+export interface StallApiResponse {
+  id: string
+  wallet: string
+  name: string
+  currency: string
+  shipping_zones: Array<{
+    id: string
+    name: string
+    cost: number
+    countries: string[]
+  }>
+  config: {
+    image_url?: string
+    description?: string
+  }
+  pending: boolean
+  event_id?: string
+  event_created_at?: number
+}
+
 export type OrderStatus = 'pending' | 'paid' | 'shipped' | 'delivered' | 'cancelled' | 'processing'
 
 export type PaymentMethod = 'lightning' | 'btc_onchain'

src/modules/market/views/CheckoutPage.vue

@@ -349,8 +349,8 @@ const orderTotal = computed(() => {
 const availableShippingZones = computed(() => {
   if (!currentStall.value) return []
   
-  // Check if stall has shipping_zones (LNbits format) or shipping (nostr-market-app format)
-  const zones = currentStall.value.shipping_zones || currentStall.value.shipping || []
+  // Use standardized shipping property from domain model
+  const zones = currentStall.value.shipping || []
   
   // Ensure zones have required properties and determine shipping requirements
   return zones.map(zone => {