fix(build): unblock SDK 56 Android + iOS builds

- app.json: kotlinVersion 2.0.21 -> 2.1.20 (Expo SDK 56 modules require >= 2.1.20)
- re-add @react-navigation/native: it is a peer dependency of
  @bottom-tabs/react-navigation and was wrongly removed; its absence broke the
  iOS eager JS bundle (expo export:embed) during the native build.

Local `expo export -p ios` now bundles cleanly. SDK 56 disables USE_FRAMEWORKS
for RNScreens/ReactCodegen, which resolves the original signed-iOS RNScreens
static-frameworks build failure.

package.json

@@ -35,6 +35,7 @@
     "@gorhom/bottom-sheet": "5.2.8",
     "@jellyfin/sdk": "^0.13.0",
     "@react-native-community/netinfo": "^12.0.0",
+    "@react-navigation/native": "^7.2.5",
     "@shopify/flash-list": "2.0.2",
     "@tanstack/query-sync-storage-persister": "^5.90.18",
     "@tanstack/react-pacer": "^0.19.1",