fix(mobile): set pnpm node-linker=hoisted for Metro bundler compatibility

Metro cannot resolve react-native internal modules (e.g. LaunchArguments)
through pnpm's default symlinked node_modules layout. Setting node-linker
to hoisted creates a flat layout that Metro can traverse, which is the
official recommendation for Expo/RN projects using pnpm.

Fixes iOS and Android CI build failures:
  "LaunchArguments.js does not exist. Falling back to file-based resolution"
  ** BUILD FAILED **

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: gsanchezm

frontend-mobile/.npmrc

@@ -0,0 +1 @@
+node-linker=hoisted