chore(mobile): upgrade Expo SDK 54 and fix external-device runtime

[mnaimfaizy]

Summary

• upgrade mobile app to Expo SDK 54-compatible dependency set
• align React/React Native/navigation packages to eliminate duplicate context/runtime conflicts
• fix external-device API URL resolution (avoid localhost/10.0.2.2 on physical devices)
• add dev:mobile:external tunnel workflow for Expo Go QR use
• update mobile test setup for React 19 compatibility

Key Changes

• apps/mobile/package.json and root package.json: SDK 54 dependency alignment
• apps/mobile/services/api.ts: robust base URL resolution + developer warnings for unreachable local URLs on devices
• apps/mobile/project.json and root scripts: improved external-device startup path
• apps/mobile/components/__tests__/ThemedText-test.tsx: migrate brittle snapshot assertion to stable RTL assertion
• remove obsolete snapshot file for ThemedText

Validation

• npx expo-doctor@latest (from apps/mobile) -> 16/16 checks passed
• yarn nx test mobile -> passing
• yarn dev:mobile:external -> QR and exp://... tunnel URL shown
• API connectivity path verified against local endpoint (/api/settings) and mobile URL fallback logic

Notes

• This branch includes lockfile changes required for SDK 54 alignment.
• Existing workspace warnings unrelated to this change (general peer warnings) are not addressed in this PR.