fix: store URL を store.posimai.soar-enrich.com に統一

Made-with: Cursor

server.js

@@ -250,7 +250,7 @@ async function purchaseMiddleware(req, res, next) {
         }
         return res.status(402).json({
             error: '購入が必要です',
-            store_url: 'https://posimai-store.vercel.app/index-c.html'
+            store_url: 'https://store.posimai.soar-enrich.com/index-c.html'
         });
     } catch (e) {
         console.error('[Purchase] DB error:', e.message);