feat: add bundle feature with 2x/3x set options

- Created BundleSelector component for selecting bundle options
- Updated ProductDetail to show bundle options
- Added bundle translations for all 4 locales
- Added GraphQL query for bundle products
- Updated TypeScript types for attributes
- Saleor backend: created bundle products for all base products

src/i18n/messages/sr.json

@@ -341,6 +341,13 @@
     "urgency2": "U korpama 2.5K ljudi - kupi pre nego što nestane!",
     "urgency3": "7.562 osobe su pogledale ovaj proizvod u poslednja 24 sata!"
   },
+  "Bundle": {
+    "selectBundle": "Izaberi pakovanje",
+    "singleUnit": "1 komad",
+    "xSet": "{count}x Set",
+    "save": "Štedi {amount}",
+    "perUnit": "po komadu"
+  },
   "Newsletter": {
     "stayConnected": "Ostanite povezani",
     "joinCommunity": "Pridružite se našoj zajednici",