feat: API route GET /api/sync/preview (TDD)

src/app/api/sync/preview/route.ts

@@ -0,0 +1,19 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { readSheetProducts } from '@/lib/googleSheets'
+import { fetchAllShopifyProducts } from '@/lib/shopifySync'
+import { computeDiff } from '@/lib/syncDiff'
+
+export async function GET(_req: NextRequest) {
+  try {
+    const [sheetProducts, shopifyProducts] = await Promise.all([
+      readSheetProducts(),
+      fetchAllShopifyProducts(),
+    ])
+
+    const diff = computeDiff(sheetProducts, shopifyProducts)
+    return NextResponse.json(diff)
+  } catch (err) {
+    const message = err instanceof Error ? err.message : 'Erreur inconnue'
+    return NextResponse.json({ error: message }, { status: 500 })
+  }
+}