Buy on StoreKit and Play Billing, then confirm with the backend (#78).

Native purchases replace RevenueCat. The app sends the signed transaction or Play token to /monetization/store/confirm/ so access is granted only after the store check.

llm-fe/package.json

@@ -11,12 +11,12 @@
     "@capacitor/keyboard": "^7.0.6",
     "@capacitor/preferences": "^7.0.4",
     "@capacitor/status-bar": "^7.0.6",
+    "native-store-billing": "file:plugins/native-store-billing",
     "@emotion/cache": "^11.14.0",
     "@emotion/react": "^11.14.0",
     "@emotion/styled": "^11.14.0",
     "@mui/icons-material": "^5.16.11",
     "@mui/material": "^5.16.11",
-    "@revenuecat/purchases-capacitor": "^11.3.2",
     "@testing-library/jest-dom": "^6.6.3",
     "@testing-library/react": "^16.1.0",
     "@testing-library/user-event": "^14.5.2",