Initialize Expo mobile app with tab navigation and monorepo support

- Expo managed project at apps/mobile/ with TypeScript
- Expo Router with 4 tabs: Map, Routes, Activities, Profile
- app.config.ts with monorepo experiment, bundle IDs, scheme
- Workspace packages linked: api, gpx, i18n, map-core, types
- Profile tab imports API_VERSION from @trails-cool/api to verify
  shared package resolution

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/mobile/.gitignore

@@ -0,0 +1,41 @@
+# Learn more https://docs.github.com/en/get-started/getting-started-with-git/ignoring-files
+
+# dependencies
+node_modules/
+
+# Expo
+.expo/
+dist/
+web-build/
+expo-env.d.ts
+
+# Native
+.kotlin/
+*.orig.*
+*.jks
+*.p8
+*.p12
+*.key
+*.mobileprovision
+
+# Metro
+.metro-health-check*
+
+# debug
+npm-debug.*
+yarn-debug.*
+yarn-error.*
+
+# macOS
+.DS_Store
+*.pem
+
+# local env files
+.env*.local
+
+# typescript
+*.tsbuildinfo
+
+# generated native folders
+/ios
+/android