Refactor mobile to fix dependency resolution and add polyfills

Update Expo and React dependencies to compatible versions. Create a
custom Metro config to resolve module conflicts in the workspace and
map Jest modules to local node_modules.

Add a SharedArrayBuffer polyfill for older runtimes and introduce an
adapter for expo-notifications to abstract direct imports.

package.json

@@ -17,6 +17,6 @@
     "typecheck:mobile": "npm run typecheck -w apps/mobile"
   },
   "overrides": {
-    "react-test-renderer": "19.2.4"
+    "react-test-renderer": "19.1.0"
   }
 }